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Joint DPPA and AMOS Seminar

Date:
18
Monday
October
2021
Lecture / Seminar
Time: 12:30
Title: Precision measurements in exotic atoms
Location: https://weizmann.zoom.us/j/93725660956?pwd=L1hOZXhkR0VLb0s4ckl0NzFqS09KUT09
Lecturer: Ben Ohayon
Organizer: Faculty of Physics
Details: 12:10 Sandwiches and more...
Abstract: Bound exotic systems offer unique opportunities to test our understanding of the ... Read more Bound exotic systems offer unique opportunities to test our understanding of the tenets of modern physics and determine fundamental constants. By comparing measured transitions between antihydrogen and hydrogen, we can search for CPT violation, which may explain the observed baryon asymmetry in the universe while respecting the stringent bounds on CP violation within the standard model. The comparison of the energy levels of muonium (M) with their clean theoretical prediction searches for new physics in a multitude of scenarios such as Lorentz and CPT violation in the muonic sector, and new bosons coupled to leptons. Such particles are motivated by the persistent discrepancy between the recently remeasured anomalous magnetic moment of the muon and its theoretical prediction, arguably the most promising hint to new physics in decades. In this talk I will review ongoing work for antihydrogen and M spectroscopy at CERN and PSI, and present our recent measurement of the Lamb-Shift in M, comprising an order of magnitude of improvement upon the state of the art and the first improvement to M energy levels in 20 years. I will conclude by showing that pushing M spectroscopy to its limits could independently determine the muon g-2 with enough accuracy to shed light on the puzzle.
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Photosynthetic energy transfer at the quantum/classical border

Date:
25
Monday
October
2021
Colloquium
Time: 11:00-12:15
Location: https://weizmann.zoom.us/j/98063488104?pwd=N3VqTC9sU1A4RHVDZ1dhOGVxbU1iUT09
Lecturer: Prof. Yossi Paltiel
Organizer: Faculty of Chemistry

Induced topological states and phases in quantum matter

Date:
10
Sunday
April
2022
-
14
Thursday
April
2022
Conference
Time: 08:00
Location: David Lopatie Conference Centre

    Past

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    Developing first-principles methods to study force- and stress-enabled mechanochemistry

    Date:
    19
    Monday
    July
    2021
    Colloquium
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Andrew M. Rappe
    Organizer: Faculty of Chemistry
    Abstract: A wide variety of chemical transformations can be induced by the application of ... Read more A wide variety of chemical transformations can be induced by the application of force or stress to reactive systems. In some cases, these reactions are undesired, including some tribochemical (friction-induced) reactions and bond-breaking in polymers under stress. A large and growing set of examples shows that mechanochemistry can be harnessed for useful chemical transformations, making the case for mechanochemistry as a general-purpose tool to advance chemical innovation. In order to realize this vision, we require greater understanding of how force and stress can be focused on particular bonds and reaction coordinates, and how this enhances chemical reactivity and selectivity. In this talk, I will outline strategies for applying stress to quantum-mechanical models of reactive chemical systems and for understanding the resulting mechanochemical reaction pathways. I will also describe the development of interatomic potential models that can enable larger-scale models of mechanochemical and piezoelectric effects in molecules, 2D materials, and polar solids.
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    Inferring Mars' Surface Winds by Analyzing the Global Distribution of Barchan Dunes using a Convolutional Neural Network

    Date:
    29
    Tuesday
    June
    2021
    Lecture / Seminar
    Time: 10:00-11:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Lior Rubanenko
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Sand seas on Mars are riddled with eolian landforms created by accumulating sand ... Read more Sand seas on Mars are riddled with eolian landforms created by accumulating sand particles. When the sand supply is limited and the wind is approximately unidirectional, these landforms take the shape of crescentic barchan dunes, whose slip-faces are approximately perpendicular to the dominant wind direction, and their horns are oriented downwind. The morphology of barchan dunes is thus routinely used to infer wind conditions on Mars by manually analyzing aerial or satellite imagery. Despite the effectiveness of this technique on a local scale, employing it on a global scale remained challenging thusfar - as manually outlining individual dunes globally is impractical, and automatic detection methods have been largely ineffective at accurately segmenting dunes in images. Here we use Mask R-CNN, an instance segmentation convolutional neural network, to detect and outline dunes globally on Mars in images obtained by the Mars Reconnaissance Orbiter Context Camera (MRO CTX). We measure the morphometrics of dunes from their detected outlines, and infer the direction of the winds that formed them. By comparing the global wind distribution we derived to a global climate model, we study Mars' past and recent climate, and constrain global sand mobility thresholds which offer insight into the erosion and dust lifting capabilities of the atmosphere of the Red Planet.
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    ULTRASAT: Revolutionizing our view of the transient universe

    Date:
    17
    Thursday
    June
    2021
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/94477142638?pwd=aWNlZGVzNmdJdnJVZVNZUi9sZ0VBZz09
    Lecturer: Eli Waxman
    Organizer: Faculty of Physics
    Details: 11:00 - Coffee, Tea and more
    Abstract: ULTRASAT is a scientific satellite, that is planned to be launched to a geo-stat ... Read more ULTRASAT is a scientific satellite, that is planned to be launched to a geo-stationary orbit in Q4 2024. It will carry a telescope with an unprecedentedly large field of view (200 squared degrees) and UV (220-280nm) sensitivity. These unique properties will enable us to detect and systematically study transient astronomical events within an extra-Galactic volume, that is hundreds of time larger than that accessible to current observatories. ULTRASAT’s measurements will have a broad science impact across the fields of gravitational wave sources, supernovae, variable and flare stars, active galactic nuclei, tidal disruption events, compact objects, and galaxies. In this talk I will review ULTRASAT’s key science goals, its unique technical properties, and the project’s structure and status.
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    Deposition of Gypsum Deltas at the Holocene Dead Sea by outsalting and paleoclimatic insights

    Date:
    27
    Tuesday
    April
    2021
    Lecture / Seminar
    Time: 10:00-11:00
    Location: https://weizmann.zoom.us/j/7621438333?pwd=c0lpdlQzYSthellXWG9rZnM0ZDRFZz09
    Lecturer: Nurit Weber
    Organizer: Department of Earth and Planetary Sciences
    Abstract: The rapid retreat of the Dead Sea during the past decades led the exposure of un ... Read more The rapid retreat of the Dead Sea during the past decades led the exposure of unique structures of massive gypsum and aragonite crusts: large capes pointing towards the open lake (termed here “gypsum deltas”) and numerous small gypsum mounds scattered on the lake’s exposed shores. Geological field relations, 14C and 34S measurements and thermodynamic calculations provide evidence that the gypsum deltas and the mounds were formed during time-intervals of low lake stands (~420±10 m below mean sea level), when sulfate-rich Ca-chloride brines discharged from the coastal aquifer via saline springs, mixed with the Dead Sea brine and precipitated the gypsum. This mixing process describes a mechanism of “gypsum outsalting”, which is completely different from the conventional view of gypsum as a product of evaporative deposition. Condition for enhanced saline springs discharge and “gypsum outsalting” occurred in the mid to late Holocene period (~ 6.6 to 0.6 ka), and were mainly intensive at the latest stages of regional aridity cycles when lake level was still low and the Dead Sea salinity was at its highest. The ages of formation of the gypsum structures coincide with times of North Atlantic cooling events and grand solar minima suggesting a direct impact of the latter on the Dead Sea hydrology and high sensitivity of the regional hydrology (controlling lake level) to global solar-related events. The frequency of appearance of the gypsum structures seems to follow the Hallstat Cycle that approached minimum at ~3000 2000 years ago.
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    Atmospheric Dynamics on Jupiter: New Results from the Juno Mission

    Date:
    22
    Thursday
    April
    2021
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/94477142638?pwd=aWNlZGVzNmdJdnJVZVNZUi9sZ0VBZz09
    Lecturer: Yohai Kaspi
    Organizer: Faculty of Physics
    Abstract: NASA's Juno Mission is now completing its 5 year nominal mission around Jupiter, ... Read more NASA's Juno Mission is now completing its 5 year nominal mission around Jupiter, orbiting the planet in an eccentric polar-orbit every 53 days. One of the prime mission objectives is better understanding the atmospheric dynamics through gravitational, microwave, infrared and magnetic measurements. In this talk, we will focus on three new results explaining different aspects of the dynamics on Jupiter. First, infrared imaging data revealed that Jupiter’s poles are surrounded by 5 cyclones around the North Pole and 8 cyclones around the South Pole. We explain the location, size and stability of these circumpolar cyclones based on vorticity dynamics. Second, using microwave data, revealing Jupiter’s deep ammonia abundance structure, we show that Jupiter has 8 meridional circulation cells in each hemisphere. These cells resemble in their governing physics Earth's midlatitude Ferrel cells, and relate to the observed red and white belts and zones at Jupiter’s cloud-level. Finally, using Juno’s gravity measurements we constrain the depth of Jupiter’s east-west jet-streams, and the depth (mass) of the most iconic vortex in the Solar system — Jupiter’s Great Red Spot. Overall, this unique multiple instrument dataset allows now explaining the governing physics of several outstanding aspects of Jupiter’s internal and atmospheric dynamics. We will also compare the dynamics to those of Saturn, generalizing some of the this new understanding.
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    Advances of remote sensing in agriculture and forestry for climate change adaptation

    Date:
    06
    Tuesday
    April
    2021
    Lecture / Seminar
    Time: 00:00
    Lecturer: Tarin Paz-Kagan
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Forests and agricultural orchards are becoming increasingly susceptible to droug ... Read more Forests and agricultural orchards are becoming increasingly susceptible to drought, ‎insect ‎‎outbreaks, and disease due to climate change worldwide. Thus, forest ‎and ‎agricultural systems management needs to be proactively targeted to improve their ‎resilience to anthropogenic and ‎climate change. The potential of remote sensing ‎data for ‎agriculture and forestry has long been recognized. The global coverage and repositories of different ‎types ‎of satellite data extending integrating with developing UAVs and ‎sensor ‎capabilities provide a unique database, which allows us to develop, test, and ‎implement ‎innovative measures to adapt agriculture and forest to the foreseen climate ‎scenarios. ‎However, there is still a considerable gap between data and information. ‎Remote sensing ‎applications integrated with innovative artificial intelligence techniques ‎could make ‎fundamental discoveries for sustainable environmental management. Thus, ‎the seminar ‎aims to present advanced remote-sensing applications for agriculture and ‎forest to climate ‎change adaptation. Four case studies will be presented, including (1) ‎mapping woody ‎species distribution and richness along the climatic gradient; (2) ‎developing canopy ‎geometry traits to characterize and monitor tree structure using LiDAR ‎applications; and (3) ‎Incorporation winter tree physiology in deciduous orchard into ‎forecast- models of bloom ‎and yield, and (4) leaf to landscape approach to study ‎forest responses to drought.
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    Simulating Chemistry from Atoms to Devices: Next-Generation Reactive Molecular Dynamics

    Date:
    31
    Sunday
    January
    2021
    Lecture / Seminar
    Time: 14:00-15:00
    Lecturer: Dr. David Furman
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Zoom Link: https://weizmann.zoom.us/j/97142508810?pwd=S2Voc3BMYnh6RmFTYUxLbU ... Read more Zoom Link: https://weizmann.zoom.us/j/97142508810?pwd=S2Voc3BMYnh6RmFTYUxLbUFjQXRGZz09 Until recently, computational studies of chemical reactivity were exclusively dealt with using quantum mechanical approaches, which severely limited the system's size and accessible time scales for simulation. To bypass the need to solve Schrodinger's equation, and facilitate large-scale simulations for up to millions of atoms, both accurate and efficient models of the chemical bond have to be constructed. I will present recent advances in the field of modeling chemical reactions in large-scale, complex systems (i.e. "dirty chemistry"), with a particular focus on ReaxFF reactive molecular dynamics. Prominent applications from recent years will be highlighted, including: (a) discovery of the underlying operation principles of a novel laser-based mass-spectrometry technique, and (b) prediction of the surprising chemistry that leads to the formation of several key precursors to biomolecules of life upon the collapse of a "primordial bubble". Finally, I will present a new ReaxFF formulation that opens exciting new avenues for orders of magnitude more accurate simulations for long time scales.
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    New perspectives on interlayer excitons in two-dimensional heterostructures

    Date:
    19
    Tuesday
    January
    2021
    Lecture / Seminar
    Time: 18:00-19:00
    Lecturer: Dr. Ouri Karni
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Zoom: https://weizmann.zoom.us/j/96278790117?pwd=T1ZjaHlxQjlEQkFIbE12UDJCaz ... Read more Zoom: https://weizmann.zoom.us/j/96278790117?pwd=T1ZjaHlxQjlEQkFIbE12UDJCazNwZz09 Two-dimensional layered (van-der-Waals) heterostructures, made by stacking different monolayers of semiconducting transition-metal dichalcogenides, have been drawing much attention as versatile platforms for studying fundamental solid-state phenomena and for designing opto-electronic devices. Interlayer excitons, electron-hole pairs that bind to each other across the interlayer spacing in these heterostructures, hold promise as key tools for probing the interlayer interface structure, and for exploring many-body interactions(1). With long lifetimes, spin polarization, and electric tunability, interlayer excitons are also promising as flexible information carriers(2, 3). However, they were mostly studied through the scope of their visible light emission, missing essential properties such as their momentum-space image or their absorption strength, necessary for rigorous study of their many-body interactions and potential applications. In this talk I will present our recent studies aimed at measuring such unknown interlayer exciton properties and their dependence on the heterostructure. I will show a new interlayer exciton in WSe2/MoS2 heterostructures which we discovered based on its light emission in infra-red wavelengths, rather than in the visible range(4). I will demonstrate its properties as inferred from its optical interrogation. Then, I will present the quantitative measurement of the elusive optical absorption spectrum of interlayer excitons using electric-field modulation spectroscopy, essential for coherent coupling of light to those excitons(5). Finally, I will reveal how time- and angle-resolved photoemission spectroscopy is used to image the interlayer exciton in momentum-space, yielding its size and binding energy, so far inaccessible through optics(5).
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    From design to optical properties in colloidal semiconductor nanocrystals

    Date:
    28
    Monday
    December
    2020
    Colloquium
    Time: 11:00-12:00
    Location: https://weizmann.zoom.us/j/98063488104?pwd=N3VqTC9sU1A4RHVDZ1dhOGVxbU1iUT09
    Lecturer: Prof. Dan Oron
    Organizer: Faculty of Chemistry
    Abstract: Colloidal semiconductor nanocrystals have turned over the past three decades fro ... Read more Colloidal semiconductor nanocrystals have turned over the past three decades from a scientific curiosity to a component in numerous commercial products, particularly in displays, lighting and light detection. On the one hand these are complex chemically synthesized entities, and on the other they behave, in many senses, as ‘giant’ artificial atoms. The interplay between these two enables us to imbue them with unique optical properties by design of their internal structure. I will go over some of our recent efforts in utilizing designer nanocrystals for various applications, including luminescence upconversion (the conversion of two low energy photons into a single high energy photon), electric field sensing and optical gain. Finally, I will discuss opportunities for the development of colloidal sources of non-classical states of light and our recent advances in quantum spectroscopy, enabling to study the optical and electronic properties of single quantum dots with unprecedented precision.
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    Israel Physics Colloquium

    Date:
    07
    Monday
    December
    2020
    Colloquium
    Time: 16:00-17:15
    Title: Emergent Gauge Fields and Topology in Quantum Matter
    Location: https://weizmann.zoom.us/j/93903178346?pwd=VUJNa0Z1NkZhZDhjTnRXeVVGbEszUT09
    Lecturer: Ashvin Vishwanath
    Organizer: Faculty of Physics
    Details: Meeting ID: 939 0317 8346 Passcode: 326163 Prior to the talk, we will have 1 ... Read more Meeting ID: 939 0317 8346 Passcode: 326163 Prior to the talk, we will have 10 minutes of socializing.
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    Abstract: For decades, condensed matter systems have been studied within the framework of ... Read more For decades, condensed matter systems have been studied within the framework of classical order parameters - i.e. the Landau-Wilson paradigm. This has been recently extended with the rather complete understanding of topological states of noninteracting electrons. In this talk I will focus instead on new physics that arises from the interplay of topology and strong interactions. A unifying theme will be the emergence of gauge fields rather than the classical order parameters of Landau theory. I will illustrate these general themes with two recent works. The first proposes a route to realizing a long sought after phase - the Z2 quantum spin liquid - in a synthetic platform, an array of highly excited (Rydberg) atoms [1]. A potential application to the engineering of naturally fault tolerant quantum bits will also be described. The second example describes a topological route to strong coupling superconductivity [2], which was inspired by recent experimental observations in magic angle bilayer graphene and related devices. [1] arXiv:2011.12310. Prediction of Toric Code Topological Order from Rydberg Blockade. Authors: R. Verresen, M. Lukin and A. Vishwanath. [2]arXiv:2004.00638. Charged Skyrmions and Topological Origin of Superconductivity in Magic Angle Graphene. Authors: E. Khalaf, S. Chatterjee, N. Bultinck, M. Zaletel, A. Vishwanath.
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    IPC - Novel Probes of Dark Matter

    Date:
    23
    Monday
    November
    2020
    Colloquium
    Time: 16:00-17:15
    Title: Israel Physics Colloquium
    Location: http://weizmann.zoom.us/j/5065402023
    Lecturer: Cora Dvorkin
    Organizer: Faculty of Physics
    Details: 16:00-16:10 Virtial Coffee Meeting ID: 939 0317 8346 Password: 326163
    Abstract: Cosmological observations and galaxy dynamics seem to imply that 84% of all matt ... Read more Cosmological observations and galaxy dynamics seem to imply that 84% of all matter in the universe is composed of dark matter, which is not accounted for by the Standard Model of particles. The particle nature of dark matter is one of the most intriguing puzzles of our time. The wealth of knowledge which is and will soon be available from cosmological surveys will reveal new information about our universe. I will discuss how we can use new and complementary data sets to improve our understanding of the particle nature of dark matter. In particular, galaxy-scale strong gravitational lensing provides a unique way to detect and characterize dark matter on small scales. I will present advances in the analysis of gravitational lenses and identification of small-scale clumps using machine learning. I will introduce the convergence power spectrum as a promising statistical observable that can be extracted from strongly lens images and used to distinguish between different dark matter scenarios, showing how different properties of the dark matter get imprinted at different scales. I will also discuss the different contribution of substructure and line-of-sight structure to perturbations in strong lens images.
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    Zoom: MSc thesis defense: Guided CdTe Nanowires: Synthesis, Structure, Optoelectronics and Bandgap Narrowing

    Date:
    23
    Monday
    November
    2020
    Lecture / Seminar
    Time: 14:00-15:30
    Lecturer: Yarden Daniel
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: https://weizmann.zoom.us/j/99592122461?pwd=MjM4ZDN0ZDFVeGZOYkdqQi9CUy9uUT09 ... Read more https://weizmann.zoom.us/j/99592122461?pwd=MjM4ZDN0ZDFVeGZOYkdqQi9CUy9uUT09 Semiconductor nanowires (NWs) are quasi 1D nanostructures, exhibiting distinctive physical properties suitable for efficient bottom-up design of nanodevices. A challenging limiting step of their integration into planar functional systems is the difficulty to align them on horizontal surfaces. One simple and elegant way to avoid post growth assembly of NWs is to grow them horizontally in the first place. Over the past decade, our group has established the surface guided growth of horizontal semiconductor NWs aligned by crystalline substrates with controlled crystallographic orientations, directions and position. As the NWs are comprised of different semiconductors, they are optically active is different spectral regimes including the UV and visible range. However, optical activity in the pivotal infrared (IR) regime is not yet exhibited for guided NWs and a systematic exploration of it can pave the way for effective devices for telecommunication and night vision technologies. CdTe, a narrow band-gap II-VI semiconductor (~1.5 eV), is an attractive candidate owing to its promising optical and electrical properties, making it an attractive material for solar cells and near IR (NIR) photodetectors. Its alloys with mercury, known as MCT (HgxCd1-xTe) are already central components of efficient IR photodetectors due to continuous bandgap narrowing with growing percentage of mercury. In this work, we present the vapor-liquid-solid (VLS) growth and self-alignment of surface guided CdTe NWs with a wurtzite crystal structure on flat and faceted sapphire substrate (α-Al2O3). The NWs were integrated into fast IR photodetectors showing high on/off ratio of up to ~104 and, to the best of our knowledge, the shortest response times (~100 ms) to IR irradiation with respect to other CdTe based photodetectors. Attempts to create HgxCd1-xTe through cation exchange show initial conversion (~2%) of the crystal, though with significant bandgap narrowing of ~ 55 meV. These findings pave the way for simple and elegant fabrication of CdTe NWs’ based NIR nano-photodetectors, which can be expended to a wide range of Mid-IR and Far-IR photodetectors with small size through bandgap engineering.
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    Bringing noble-gas spins into the light

    Date:
    19
    Thursday
    November
    2020
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/92790893230?pwd=VlRjVzkvaGZ5YWRvcXFGWXVXZ3dXdz09
    Lecturer: Ofer Firstenberg
    Organizer: Faculty of Physics
    Abstract: In quantum science, we often encounter the tension between elongating the cohere ... Read more In quantum science, we often encounter the tension between elongating the coherence time of a system and retaining the ability to control and interact with it. An extreme example is the nuclear spin of noble gases, which is isolated from the environment by the complete electronic shells. In our lab, the spins of a helium-3 gas maintain coherence for up to two hours. Unfortunately, these spins are not accessible to light in the optical domain, and their (potential) quantum qualities have been beyond reach and largely overlooked. We establish that thermal spin-exchange collisions between noble-gas atoms and alkali-metal atoms form a quantum interface between them. These weak collisions, despite their stochastic nature, accumulate to a deterministic, efficient, and controllable coupling between the collective spins of the two gases. In experiments, we realize the strong coupling between potassium and helium-3 spins and, by coupling light to the potassium spins, demonstrate an efficient, two-way, optical interface to the helium-3 spins. The interface paves the way to employing noble-gas spins in the quantum domain, and we discuss prospects for quantum memories and entanglement of distant noble-gas ensembles with hour-long lifetimes.
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    IPC - Nov 09 - Jesse Thaler

    Date:
    09
    Monday
    November
    2020
    Colloquium
    Time: 16:00-17:15
    Title: דיווחים
    Location: https://weizmann.zoom.us/j/93903178346?pwd=VUJNa0Z1NkZhZDhjTnRXeVVGbEszUT09
    Lecturer: Jesse Thaler
    Organizer: Faculty of Physics
    Details: Zoom Link- https://weizmann.zoom.us/j/93903178346?pwd=VUJNa0Z1NkZhZDhjTnRXeVVGbE ... Read more Zoom Link- https://weizmann.zoom.us/j/93903178346?pwd=VUJNa0Z1NkZhZDhjTnRXeVVGbEszUT09 Meeting ID: 939 0317 8346 Password: 326163
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    Abstract: Collision Course: Particle Physics meets Machine Learning Modern machine le ... Read more Collision Course: Particle Physics meets Machine Learning Modern machine learning has had an outsized impact on many scientific fields, and particle physics is no exception. What is special about particle physics, though, is the vast amount of theoretical and experimental knowledge that we already have about many problems in the field. In this colloquium, I present two cases studies involving quantum chromodynamics (QCD) at the Large Hadron Collider (LHC), highlighting the fascinating interplay between theoretical principles and machine learning strategies. First, by cataloging the space of all possible QCD measurements, we (re)discovered technology relevant for self-driving cars. Second, by quantifying the similarity between two LHC collisions, we unlocked a class of nonparametric machine learning techniques based on optimal transport. In addition to providing new quantitative insights into QCD, these techniques enable new ways to visualize data from the LHC.
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    Online Israel Physics Colloquium: "The magic of moiré quantum matter"

    Date:
    26
    Monday
    October
    2020
    Colloquium
    Time: 16:00-17:15
    Location: https://weizmann.zoom.us/j/93903178346?pwd=VUJNa0Z1NkZhZDhjTnRXeVVGbEszUT09
    Lecturer: Pablo Jarillo-Herrero
    Organizer: Faculty of Physics
    Abstract: The understanding of strongly-correlated quantum matter has challenged physicist ... Read more The understanding of strongly-correlated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, namely moiré quantum matter. In particular, I will show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly-correlated electronic system. These flat bands systems exhibit a plethora of quantum phases, such as correlated insulators, superconductivity, magnetism, Chern insulators, and more. Furthermore, it is possible to extend the moiré quantum matter paradigm to systems beyond magic angle graphene, and I will present an outlook of some exciting directions in this emerging field.
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    From Ultralight Dark Matter to Snowballs in Hell: a Tour in Particle Astrophysics

    Date:
    22
    Thursday
    October
    2020
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/92790893230?pwd=VlRjVzkvaGZ5YWRvcXFGWXVXZ3dXdz09
    Lecturer: Kfir Blum
    Organizer: Faculty of Physics
    Abstract: Astrophysical phenomena play a definitive role in our understanding of fundament ... Read more Astrophysical phenomena play a definitive role in our understanding of fundamental particle physics, and vice-verse. I will present two lines of research, showcasing the interplay between particle physics theory and astrophysics. In the first half of the talk, I will show how the viable parameter space for dark matter can be established using gravity alone. At the lowest end of the possible range for the dark matter particle mass, the de Broglie wavelength of ultralight dark matter (ULDM) attains astronomical scales. The ensuing wave mechanics phenomena can be tested observationally in a variety of astrophysical systems. I will describe a search for the imprint of ULDM on the gas kinematics of low-surface-brightness galaxies, leading to an absolute lower bound on the mass of dark matter. A host of other systems, ranging from supermassive black holes to gravitational lensing, offer promising means to advance the search for ULDM by orders of magnitude. In the second half of the talk, I will show how an analysis of cosmic ray antimatter — long considered a smoking gun for dark matter in the TeV range — has taken a surprising turn, leading us to new theoretical insights on the problem of the origin of loosely-bound nuclei in hadronic collisions (sometimes referred to as ``Snowballs in Hell”). The resulting research programme, now explored at the Large Hadron Collider, offers a bridge between two-particle correlation analyses to the study of nuclear clusters.
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    Lifshitz theory of the cosmological constant

    Date:
    15
    Thursday
    October
    2020
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/92790893230?pwd=VlRjVzkvaGZ5YWRvcXFGWXVXZ3dXdz09
    Lecturer: Ulf Leonhardt
    Organizer: Faculty of Physics
    Abstract: The cosmological constant, also known as dark energy, was believed to be caused ... Read more The cosmological constant, also known as dark energy, was believed to be caused by vacuum fluctuations, but naive calculations give results in stark disagreement with fact. In the Casimir effect, vacuum fluctuations cause forces in dielectric media, which is very well described by Lifshitz theory. Recently, using the analogy between geometries and media, a cosmological constant of the correct order of magnitude was calculated with Lifshitz theory [U. Leonhardt, Ann. Phys. (New York)  411, 167973 (2019)]. This lecture discusses the empirical evidence and the ideas behind the Lifshitz theory of the cosmological constant without requiring prior knowledge of cosmology and quantum field theory.
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    Zoom lecture: Quantum sensor assisted magnetic resonance

    Date:
    15
    Thursday
    October
    2020
    Lecture / Seminar
    Time: 09:30-10:30
    Lecturer: Prof. Ashok Ajoy
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Details: Yeda Research and Development Ltd. is the commercial branch of the Weizmann Inst ... Read more Yeda Research and Development Ltd. is the commercial branch of the Weizmann Institute of Science. Yeda holds an exclusive right to commercialize the unique intellectual property developed by the scientists at the Weizmann Institute.
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    Abstract: Nuclear magnetic resonance (NMR) spectroscopy, is renowned for its high chemic ... Read more Nuclear magnetic resonance (NMR) spectroscopy, is renowned for its high chemical specificity, but suffers from low sensitivity and poor spatial resolution. This has largely locked up NMR in “central facilities”, where the measurement paradigm involves taking the sample to the NMR spectrometer. We are innovating a class of optical NMR probes that can allow one to invert this paradigm, effectively bringing the NMR spectrometer into the sample. This would open possibilities for NMR probes of analytes in their local environment. These “deployable” NMR sensors rely on a uniquely optically addressable spin platform constructed out of nanoparticles of diamonds, hosting defect centers (NV centers) and 13C nuclei. Such electron-nuclear spin hybrids serve dual-roles as optical “polarization injectors” and optical NMR detectors while also being targetable to within the sample of interest. I will focus on the main ingredients of this technology, while alluding to potential frontier applications opened as a result. Zoom link: https://weizmann.zoom.us/j/98496818322?pwd=RW03TWtTUUpKYXBXQlJtbnprMTRKdz09 passcode: 888482
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    Visualizing Strongly-Interacting Quantum Matter

    Date:
    24
    Thursday
    September
    2020
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/92790893230?pwd=VlRjVzkvaGZ5YWRvcXFGWXVXZ3dXdz09
    Lecturer: Shahal Ilani
    Organizer: Faculty of Physics
    Abstract: When quantum mechanics and Coulomb repulsion are combined in a pristine solid, s ... Read more When quantum mechanics and Coulomb repulsion are combined in a pristine solid, some of the most fascinating electronic phases in nature can emerge. Interactions between electrons can form correlated insulators, electronic liquids, and in extreme cases even quantum electronic solids. These phases are predicted to exhibit their most striking features in real-space, however, they are also extremely fragile, preventing their visualization with existing experimental tools. In this talk, I will describe our experiments that use a pristine carbon nanotube as a new type of a scanning probe, capable of imaging electrical charge with unprecedented sensitivity and minimal invasiveness. I will show how using this platform we were able to obtain the first images of the quantum crystal of electrons, visualize the collective hydrodynamic flow of interacting electrons in graphene, and unravel the parent state that underlies the physics of strongly-interacting electrons in the recently-discovered system of magic angle twisted bilayer graphene.
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    Quantum Critical Metals

    Date:
    27
    Thursday
    August
    2020
    Colloquium
    Time: 11:15-12:30
    Location: https://weizmann.zoom.us/j/92790893230?pwd=VlRjVzkvaGZ5YWRvcXFGWXVXZ3dXdz09
    Lecturer: Erez Berg
    Organizer: Faculty of Physics
    Abstract: Metallic quantum critical phenomena are believed to play a key role in many stro ... Read more Metallic quantum critical phenomena are believed to play a key role in many strongly correlated materials, including high temperature superconductors. Theoretically, the problem of quantum criticality in the presence of a Fermi surface has proven to be highly challenging. However, it has recently been realized that many models used to describe such systems are amenable to numerically exact solution by quantum Monte Carlo (QMC) techniques, without suffering from the fermion sign problem. I will review the status of the understanding of metallic quantum criticality, and the recent progress made by QMC simulations. The results obtained so far will be described, as well as their implications for superconductivity, non-Fermi liquid behavior, and transport in the vicinity of metallic quantum critical points. Some of the outstanding puzzles and future directions are highlighted.
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    Coherent Network Computing 2020 (CNC2020)

    Date:
    13
    Monday
    July
    2020
    -
    16
    Thursday
    July
    2020
    Conference
    Time: 08:00
    Location: Michael Sela Adutitorium
    Organizer: Department of Physics of Complex Systems

    Real Time Quantum Sensing and Jüdisch-Deutsch

    Date:
    18
    Thursday
    June
    2020
    Lecture / Seminar
    Time: 09:30-10:30
    Lecturer: Dr. Amit Finkler
    Organizer: Clore Institute for High-Field Magnetic Resonance Imaging and Spectroscopy
    Abstract: Zoom Lecture: Link: https://weizmann.zoom.us/j/98578269625 Magnetometry on ... Read more Zoom Lecture: Link: https://weizmann.zoom.us/j/98578269625 Magnetometry on the nanoscale range stands to benefit from quantum-enhanced sensing techniques, as these can potentially overcome classical noise limits. Specifically in our group we use a single nitrogen-vacancy center as an atomic-sized quantum sensor, with uT(nT) magnetic field sensitivity for dc(ac) fields. Yet our measurement technique does rely on classical averaging due to a relatively poor signal-to-noise ratio. In this respect, a real-time response and feedback during signal acquisition based on (quantum) phase estimation promises to significantly reduce averaging time by using prior information obtained during the measurement. I will present our current efforts in this direction, with the aim of performing adaptive sensing of nanoscale magnetic fields. Both static (dc) and dynamic (ac) problems will be addressed. Finally, since this is after all a magnetic resonance seminar, I will present the relevant research context pertaining to electron spin resonance of small molecules and explain how we intend to reach the single molecule limit with this quantum sensing technology.
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    Faculty Seminar

    Date:
    25
    Monday
    May
    2020
    Lecture / Seminar
    Time: 17:30-18:30
    Title: Randomness extraction and amplification in the quantum world
    Lecturer: Rotem Arnon-Friedman
    Organizer: Faculty of Mathematics and Computer Science
    Details: Randomness is an essential resource in computer science. In most applications pe ... Read more Randomness is an essential resource in computer science. In most applications perfect, and sometimes private, randomness is needed, while it is not even clear that such a resource exists. It is well known that the tools of classical computer science do not allow us to create perfect randomness from a single weak source of randomness -
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    Chemical and Biological Physics Guest Seminar

    Date:
    30
    Thursday
    April
    2020
    Lecture / Seminar
    Time: 11:00
    Title: New Quantum Molecular Spintronics Based on Molecular Magnets: Quantum Computer and Single-Molecule Memory Performance
    Location: Perlman Chemical Sciences Building
    Lecturer: Professor Masahiro Yamashita
    Organizer: Department of Chemical and Biological Physics
    Abstract: Spintronics is a key technology in the 21st century. Although bulk magnets comp ... Read more Spintronics is a key technology in the 21st century. Although bulk magnets composed of transition metals are normally used, in our study, we use Single-Molecule Magnets (SMMs) to overcome “Moore`s Limitation”. For realizing the single-molecule memory device by using spin-polarized STM, we have succeeded to write and read the spin orientations of TbPc2 as up and down, respectively. For realizing the quantum computer, the spin Qubits and coherence at room temperature are very important. For this purpose, we synthesized monomer-Porphyrin V(IV) complex (0D) and MOF-Porphyrin V(IV) complexes (3D). The 3D complex shows Rabi nutation even at room temperature due to the rigid lattice of MOF. We have succceded the encapsulation of Metal Fulleren SMMs into SWCNT, which is new spintronics.
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    Braginsky Center for the Interface between the Sciences and the Humanities

    Date:
    27
    Monday
    April
    2020
    Lecture / Seminar
    Time: 13:00-14:00
    Title: Quantum Mechanics Making New Sense
    Location: Zoom:https://weizmann.zoom.us/j/99252264007
    Lecturer: Prof. Avshalom C. Elitzur
    Organizer: Braginsky Center for the Interface between Science and the Humanities
    Abstract: Ever since quantum mechanics has emerged, the phenomena it has revealed turned ... Read more Ever since quantum mechanics has emerged, the phenomena it has revealed turned out to be more and more alien to classical scientific reasoning, undermining basic notions like determinism and cause-and-effect relations. A novel method developed by Aharonov et al. computes the quantum process twice, once from past to future and then vice versa, backwards in time. The combined result gives a much more lucid explanation to all quantum oddities. Moreover it yields some surprising predictions, recently verified by experiments. This is an introduction to these advances and some of their bearings on other sciences
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    2020 G.M.J. SCHMIDT MEMORIAL LECTURE - Plasmonic Cavities: What are they and How they teach us quantum optics

    Date:
    27
    Monday
    April
    2020
    Lecture / Seminar
    Time: 11:00-12:15
    Title: Zoom lecture
    Location: https://weizmann.zoom.us/j/99591850435
    Lecturer: Prof. Gilad Haran
    Organizer: Faculty of Chemistry
    Details: Join the zoom lecture via this link: https://weizmann.zoom.us/j/99591850435

    Chemical and Biological Physics Special Seminar

    Date:
    26
    Sunday
    April
    2020
    Lecture / Seminar
    Time: 14:00-15:00
    Title: New Quantum Molecular Spintronics Based on Molecular Magnets: Quantum Computer and Single-Molecule Memory Performance
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Masahiro Yamashita
    Organizer: Department of Chemical and Biological Physics
    Abstract: Spintronics is a key technology in the 21st century. Although bulk magnets comp ... Read more Spintronics is a key technology in the 21st century. Although bulk magnets composed of transition metals are normally used, in our study, we use Single-Molecule Magnets (SMMs) to overcome “Moore`s Limitation”. For realizing the single-molecule memory device by using spin-polarized STM, we have succeeded to write and read the spin orientations of TbPc2 as up and down, respectively. For realizing the quantum computer, the spin Qubits and coherence at room temperature are very important. For this purpose, we synthesized monomer-Porphyrin V(IV) complex (0D) and MOF-Porphyrin V(IV) complexes (3D). The 3D complex shows Rabi nutation even at room temperature due to the rigid lattice of MOF. We have succceded the encapsulation of Metal Fulleren SMMs into SWCNT, which is new spintronics
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    CANCELLED: Braginsky Center for the Interface between the Sciences and the Humanities

    Date:
    20
    Monday
    April
    2020
    Lecture / Seminar
    Time: 15:00-16:00
    Title: "Quantum Mechanics Making New Sense"
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Avshalom C. Elitzur
    Organizer: Department of Molecular Genetics

    On energy equilibration in slow fast systems

    Date:
    16
    Monday
    March
    2020
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Vered Rom-Kedar
    Organizer: Department of Physics of Complex Systems
    Abstract: . In 1949, Fermi proposed a mechanism for the heating of particles in cosmic ray ... Read more . In 1949, Fermi proposed a mechanism for the heating of particles in cosmic rays. He suggested that on average, charged particles gain energy from collisions with moving magnetic mirrors since they hit the mirrors more frequently with heads on collisions. Fermi, Ulam and their followers modeled this problem by studying the energy gain of particles moving in billiards with slowly moving boundaries. Until 2010 several examples of such oscillating billiards leading to power-law growth of the particles averaged energy were studied. In 2010 we constructed an oscillating billiard which produces exponential in time growth of the particles energy. The novel mechanism which leads to such an exponential growth is robust and may be extended to arbitrary dimension. Moreover, the exponential rate of the energy gain may be predicted by utilizing adiabatic theory and probabilistic models. The extension of these results to billiards with mixed phase space leads to the development of adiabatic theory for non-ergodic systems. Finally, such accelerators lead to a faster energy gain in open systems, when particles are allowed to enter and exit them through a small hole. The implications of this mechanism on transport in extended systems and on equilibration of energy in closed systems like "springy billiards" will be discussed. The latter application provides a key principle: to achieve ergodicity in slow-fast systems in the adiabatic limit, the fast subsystems should NOT be ergodic.
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    Recovering Lost Information in the Digital World

    Date:
    15
    Sunday
    March
    2020
    Lecture / Seminar
    Time: 13:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Yonina Eldar, WIS
    Organizer: Department of Physics of Complex Systems
    Abstract: The conversion of physical analog signals to the digital domain for further proc ... Read more The conversion of physical analog signals to the digital domain for further processing inevitably entails loss of information.The famous Shannon-Nyquist theorem has become a landmark in analog to digital conversion and the development of digital signal processing algorithms. However, in many modern applications, the signal bandwidths have increased tremendously, while the acquisition capabilities have not scaled sufficiently fast. Furthermore, the resulting high rate digital data requires storage, communication and processing at very high rates which is computationally expensive and requires large amounts of power. In this talk, we present a framework for sampling and processing a wide class of wideband analog signals at rates far below Nyquist by exploiting signal structure and the processing task. We then show how these ideas can be used to overcome fundamental resolution limits in optical microscopy, ultrasound imaging, quantum systems and more. We demonstrate the theory through several demos of real-time sub-Nyquist prototypes and devices operating beyond the standard resolution limits combining high spatial resolution with short integration time.
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    Dwarf Galaxies as Astrophysical Laboratories

    Date:
    05
    Thursday
    March
    2020
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Josh Simon
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: The dwarf galaxies orbiting the Milky Way are the oldest, least luminous, most d ... Read more The dwarf galaxies orbiting the Milky Way are the oldest, least luminous, most dark matter-dominated, and least chemically evolved stellar systems known. To begin, I will provide a brief introduction to these galaxies, highlighting the recent discovery of large numbers of ultra-faint dwarf galaxies. I will then explain how we can measure their dark matter content and describe some of the numerous ways that dwarfs are being used to constrain the properties of dark matter. Finally, I will show how chemical abundance measurements of dwarf galaxy stars provided critical insight into r-process nucleosynthesis prior to the LIGO discovery of a neutron star merger.
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    Radiation-Dominated Black Hole Accretion Flows

    Date:
    27
    Thursday
    February
    2020
    Colloquium
    Time: 00:00
    Lecturer: James Stone
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: At high accretion rates, the outward force of radiation pressure generated by en ... Read more At high accretion rates, the outward force of radiation pressure generated by energy released by infalling matter can exceed the inward pull of gravity.  Such super-Eddington accretion flows occur in many systems, such as the inner regions of quasars and luminous AGN, ultra-luminous X-ray sources (ULXs), and tidal disruption events.  Understanding such flows is important not only for interpreting the spectra and variability of these sources, but also to predict the rate of growth of black holes in the early universe, and to quantify energy and momentum feedback into the medium surrounding the black hole, a process likely to be important in galaxy formation.  New results from a study of the magnetohydrodynamics of luminous accretion flows, in which radiation pressure dominates, will be presented. Our results reveal new physical effects, such as turbulent transport of radiation energy, that require extension of standard thin-disk models.  We discuss the implications of our results for the astrophysics of accreting black holes.
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    Highly magnified gravitationally lensed stars as a probe to the nature of dark matter

    Date:
    13
    Thursday
    February
    2020
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Jordi Miralda-Escude
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: Dark matter continues to pose one of the most important questions in modern cosm ... Read more Dark matter continues to pose one of the most important questions in modern cosmology. Gravitationally lensed multiple images of galaxies, quasars and stars provide several opportunities for testing the clumpiness of dark matter on small scales due to, for example, compact objects, axion mini-clusters and waves, or subhalos orbiting on galactic or cluster dark matter halos. The idea of using highly magnified stars by lensing clusters to probe this small-scale granularity in the dark matter will be discussed.
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    Optics, Vision, and Evolution, after Mitchell Feigenbaum 1944-2019

    Date:
    12
    Wednesday
    February
    2020
    Lecture / Seminar
    Time: 11:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Jean-Pierre Eckmann
    Organizer: Clore Center for Biological Physics
    Abstract: Many people are aware of Feigenbaum's astonishing discovery of the universality ... Read more Many people are aware of Feigenbaum's astonishing discovery of the universality of period doubling, and the constant delta=4.66920 which carries his name. In the last 13 years of his life Feigenbaum worked on other subjects, and he wrote the manuscript (in TeX) of a book whose title is "Reflections on a Tube". This is closely related to his life-long interest in optics and aspects of vision. It deals with the optics of images reflected in a cylindrical mirror (usually called anamorphic pictures). He shows that the eye does not interpret ray-tracing, but caustics. But there are two caustics, and therefore, the viewer can actually see two different images. The visual system will often prefer one over the other. The question is the "which" and "why"? Starting from this discovery, Feigenbaum derived other aspects of this observation, dealing with the vision of fish, the "broken" pencil in water, or aspects of the floor of swimming pools. All these examples show two possible images. His study tells me how a simple study in classical optics can lead to interesting questions in perception and the visual system. I will give an overview of this project. As I discussed with him, over those 13 years, many aspects of his work, I have edited his manuscript so it can be published as a book which should appear in a forseeable future.
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    Thermal conductance of one dimensional disordered harmonic chains

    Date:
    10
    Monday
    February
    2020
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Biswarup Ash - WIS
    Organizer: Department of Physics of Complex Systems
    Abstract: Heat transfer in solids is usually described in terms of Fourier's law according ... Read more Heat transfer in solids is usually described in terms of Fourier's law according to which the thermal conductance of a material scales inversely with its length or, equivalently, thermal conductivity is independent of sample length. Theoretical and experimental studies over the past decade have demonstrated that Fourier's law is violated for a variety of one-dimensional systems. Despite the large number of studies of many intriguing models, the validity criteria for Fourier's law remain elusive, and a breakdown of Fouriers law seems to be commonplace. In this talk, I will discus heat conduction mediated by longitudinal phonons in one dimensional disordered harmonic chains to understand the role of different parameters that may affect the scaling of thermal conductance in these systems. Using scaling properties of the phonon density of states and localization in disordered systems, we find non-trivial scaling of the thermal conductance with the system size. Our theoretical findings are corroborated by extensive numerical analysis. We show that, suprisingly, the thermal conductance of a system with strong disorder, characterized by a `heavy-tailed' probability distribution, and with large impedance mismatch between the bath and the system scales normally with the system size, i.e., in a manner consistent with Fourier's law. We identify a dimensionless scaling parameter, related to the temperature scale and the localization length of the phonons, through which the thermal conductance for different models of disorder and different temperatures follows a universal behavior.
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    Packets of Diffusing Particles Exhibit Universal Exponential Tails

    Date:
    09
    Sunday
    February
    2020
    Lecture / Seminar
    Time: 13:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Stas Burov
    Organizer: Department of Physics of Complex Systems
    Abstract: Brownian motion is a Gaussian process described by the central limit theorem. Ho ... Read more Brownian motion is a Gaussian process described by the central limit theorem. However, exponential decays of the positional probability density function $P(X,t)$ of packets of spreading random walkers, were observed in numerous situations that include glasses, live cells and bacteria suspensions. We show that such exponential behavior is generally valid in a large class of problems of transport in random media. By extending the Large Deviations approach for a continuous time random walk we uncover a general universal behavior for the decay of the density. It is found that fluctuations in the number of steps of the random walker, performed at finite time, lead to exponential decay (with logarithmic corrections) of $P(X,t)$. This universal behavior holds also for short times, a fact that makes experimental observations readily achievable.
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    Testing Gravity with Cold Atoms

    Date:
    06
    Thursday
    February
    2020
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Guglielmo M. Tino
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: The ability to control the quantum degrees of freedom of atoms using laser light ... Read more The ability to control the quantum degrees of freedom of atoms using laser light opened the way to precision measurements of fundamental physical quantities. I will describe experiments for precision tests of gravitational physics using new quantum devices based on ultracold atoms, namely, atom interferometers and optical clocks. I will report on the measurement of the gravitational constant G with a Rb Raman interferometer, on experiments based on Bloch oscillations of Sr atoms confined in an optical lattice for gravity measurements at small spatial scales, and on new tests of the Einstein equivalence principle. I will also discuss prospects to use atoms as new detectors for gravitational waves and for experiments in space.
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    Scale Invariance at low accelerations as an alternative to the dark Universe

    Date:
    30
    Thursday
    January
    2020
    Colloquium
    Time: 11:15-12:45
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Mordehai Milgrom
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, tea and more
    Abstract: Galactic systems and the Universe at large exhibit significant anomalies when an ... Read more Galactic systems and the Universe at large exhibit significant anomalies when analyzed within Newtonian dynamics and general relativity: Large discrepancies are found between the gravitational masses required by the observed dynamics, and the masses we actually observe in these systems. The mainstream explanation of these anomalies invokes the dominant and ubiquitous presence of “dark matter”. The "MOND" paradigm suggests, instead, that the discrepancies are due to breakdown of standard dynamics in the limit of low accelerations, where MOND dynamics are space-time scale invariant. MOND accounts for many detailed manifestations of the mass discrepancies with no need for dark matter. I will outline the paradigm, some of its achievements, and some remaining problems and desiderata.
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    The Surprises of a Nanochannel –

    Date:
    27
    Monday
    January
    2020
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Yoav Green
    Organizer: Department of Physics of Complex Systems
    Abstract: Nanofluidic systems have the potential to revolutionize numerous fields of high ... Read more Nanofluidic systems have the potential to revolutionize numerous fields of high practical importance, including desalination, energy harvesting, bio-sensing, fluid based electrical circuits, and more. It is, therefore, not surprising that in the last two decades we are witnessing an increase in nanofluidic-based research. However, realizing the full potential of nanofluidics remains conditional to conquering several significant challenges. Notably, our current understanding of the fundamental physical phenomena that govern ion transport through nanochannels is incomplete and many key questions remain open. Fifteen years ago it was suggested that low-voltage Ohmic response of nanochannel-microchannels systems was dominated by the electrical resistance of the nanochannel, and that the resistances of the adjacent microchannels, were negligible. I will present evidence contradicting this suggestion that has since become paradigm. I will present a new modified paradigm which emphasizes the importance of the microchannels in determining the overall response. Our result suggest the need to conduct fundamental driven research to further reveal the physics of ion-transport at low-voltages so that we can unveil the physics at high-voltages where non-linear electroconvective effects are prevalent. Bio: Yoav Green is currently a senior lecturer in the Department of Mechanical Engineering at Ben-Gurion University. Before that, Yoav was post-doctoral researcher in the Harvard T. H. Chan School of Public Health where he worked in the field of biomechanics. Yoav holds a PhD in mechanical engineering from the Technion - Israel Institute of Technology where his research fields were nanofluidics and electrokinetics. Yoav also holds an MSc in physics (astrophysics and astronomy) from the Weizmann Institute of Science, and BSc in aerospace engineering from the Technion.
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    Algebraic Geometry and Representation Theory Seminar

    Date:
    21
    Tuesday
    January
    2020
    Lecture / Seminar
    Time: 11:15-12:30
    Title: A bridge between p-adic and quantum group representations via Whittaker coinvariants.
    Location: Jacob Ziskind Building
    Lecturer: Valentin Buciumas
    Organizer: Faculty of Mathematics and Computer Science
    Details: Unramified principal series representations of p-adic GL(r) and its metaplectic ... Read more Unramified principal series representations of p-adic GL(r) and its metaplectic covers are important in the theory of automorphic forms. I will present a method of relating the Whittaker coinvariants of such a representation with representations of quantum affine gl_n. This involves using a Schur-Weyl duality result due to Chari and Pressley and it allows us to compute the dimension of the Whittaker model of every irreducible smooth representation with Iwahori fixed vectors. If time permits I will explain a conjectured version of this result for the symplectic group Sp(2r) which involves quantum symmetric pairs.
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    Self-assembled Electrolytes: Conserved media with non-equilibrium properties and why should we care about it?

    Date:
    20
    Monday
    January
    2020
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Arik Yochelis, BGU
    Organizer: Department of Physics of Complex Systems
    Abstract: Self-assembly driven by phase separation coupled to Coulombic interactions is fu ... Read more Self-assembly driven by phase separation coupled to Coulombic interactions is fundamental to a wide range of applications, examples of which include soft matter lithography via di-block copolymers, membrane design using poly-electrolytes, and renewable energy applications based on complex nano-materials, such as ionic liquids. I will show by using two continuum case models, ionic liquids and charged polymers, that although self-assembly in electrolytes is a gradient flow system, it surprisingly displays several fundamental features that are related to far from equilibrium (reaction-diffusion) systems and thus, allow for novel realizations, interpretations, and applications to concentrated electrolytes.
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    The reference map technique for simulating complex materials and

    Date:
    19
    Sunday
    January
    2020
    Lecture / Seminar
    Time: 13:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Christopher Rycroft
    Organizer: Department of Physics of Complex Systems
    Abstract: > Conventional computational methods often create a dilemma for fluid–structur ... Read more > Conventional computational methods often create a dilemma for fluid–structure interaction problems. Typically, solids are simulated using a Lagrangian approach with grid that moves with the material, whereas fluids are simulated using an Eulerian approach with a fixed spatial grid, requiring some type of interfacial coupling between the two different perspectives. Here, a fully Eulerian method for simulating structures immersed in a fluid will be presented. By introducing a reference map variable to model finite-deformation constitutive relations in the structures on the same grid as the fluid, the interfacial coupling problem is highly simplified. The method is particularly well suited for simulating soft, highly-deformable materials and many-body contact problems, and several examples will be presented. This is joint work with Ken Kamrin (MIT).
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    Solid State NMR of low abundant quadrupolar nuclei achieved through extended coherence lifetimes

    Date:
    16
    Thursday
    January
    2020
    Lecture / Seminar
    Time: 09:30-10:30
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Dr. Daniel Jardon-Alvarez
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Less is more! By using extremely low power refocusing π pulses in echo train se ... Read more Less is more! By using extremely low power refocusing π pulses in echo train sequences the coherence lifetime, T2, of the central transition of half-integer quadrupolar nuclei can be largely extended. This effect is particularly impactful in systems dilute in NMR active nuclei, where sources of decoherence are scarce. Crucial to this lifetime extension is the avoidance of coherence transfer to short-lived non-symmetric “killing” transitions. For 17O in polycrystalline α-quartz we were able to retain coherent magnetization for over four minutes on the transverse plane. This translates into enormous sensitivity gains for echo train acquisition after addition of the long living echoes. By combining satellite population transfer schemes with a low power CPMG on 17O in quartz, we obtain over a 1000-fold sensitivity enhancement compared to a spectrum from a free induction decay acquired at a more typical rf field strength. This enhancement allows the acquisition of a highly resolved 17O spectrum within less than one hour, despite its low natural abundance and a spin-lattice relaxation time of approximately 900 s. In this talk I will present a thorough analysis of the effects of pulse power on the echo intensity, coherence lifetime and line shape integrity. Finally, we apply this approach on various crystalline and glassy inorganic solids, including other low sensitivity nuclei, such as 33S and 45Ca, showing that it can be beneficial for a large number of systems.
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    Chemical and Biological Physics Guest Seminar

    Date:
    14
    Tuesday
    January
    2020
    Lecture / Seminar
    Time: 11:00-12:00
    Title: Emerging exotic quantum phenomena in 1D molecular chains on surfaces
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr Pavel Jelinek
    Organizer: Department of Chemical and Biological Physics
    Abstract: Low dimensional materials offer very interesting material and physical propertie ... Read more Low dimensional materials offer very interesting material and physical properties due to reduced dimensionality. Nowadays, mostly 2D materials are the focus of attention. However, 1D systems often show far more exotic behavior, such as Tomanaga-Luttinger liquid, Peierls distortion, etc.. In this talk, we will present different classes of 1D molecular chains formed on metallic surfaces by on-surface synthesis, which physical and chemical properties were investigated by low temperature UHV scanning probe microscopy supported by theoretical analysis. First, we will introduce a novel strategy to synthesize [1] a new class of intrinsically quasi-metallic one-dimensional (1D) -conjugated polymers featuring topologically non-trivial quantum states. Furthermore, we unveiled the fundamental relation between quantum topology, -conjugation and metallicity of polymers [2]. Thus, we will make a connection between two distinct worlds of topological band theory (condensed matter physics) and -conjugation polymer science (chemistry). We strongly believe this may stimulate new ways of thinking towards a design of novel organic quantum materials. In second part, we will demonstrate unusual mechanical and electronic properties of hydrogen bonded chains formed on a metallic surface driven by quantum nuclaar effects within the chain. We will show, that the concerted proton tunneling not only enhances the mechanical stability of the chain, but it also gives rise to new in-band gap electronics states localized at the ends of the chain. [1] A. Grande-Sanchez et al. Angew. Chem. Int. Ed. 131, 6631-6635 (2019). [2] B. Cierra et al arXiv preprint arXiv:1911.05514
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    Full counting and extreme value statistics for a gas of 2d charged particles

    Date:
    13
    Monday
    January
    2020
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Bertrand Lacrois-A-Chez-Toine
    Organizer: Department of Physics of Complex Systems
    Abstract: In this talk, we consider a model of 2d one component plasma, i.e. a gas of iden ... Read more In this talk, we consider a model of 2d one component plasma, i.e. a gas of identical negatively charged particles. These charges are at equilibrium at inverse temperature B in an external containing potential created by a positive charge smeared over the two dimensional plane. For specific potentials and temperatures, this problem is connected to the study of eigenvalues of non-Hermitian random matrices, to the quantum fluctuations of fermions in a rotating harmonic trap or in a Laughlin state. We study the extreme value statistics for this system as well as the full counting statistics, i.e. the number of charges in a given domain of space. For both these observables, the regime of typical fluctuations [1] and the large deviation regime [2, 3] have been characterized. While one would naively expect a smooth matching between these regimes, as it is the case for example for observables of Hermitian random matrices, it is not the case here. We solve this puzzle by showing that for both cases, an intermediate regime" of fluctuations emerges and characterize it in detail [4, 5]. This regime is universal with respect to a large class of confining potential. We have also considered potentials that do not enter this class and shown that there are cases where an intermediate regime of fluctuation does not appear. References [1] T. Shirai, J. Stat. Phys. 123, 615 (2006). [2] R. Allez, J. Touboul, G. Wainrib, J. Phys. A: Math. Theor. 47, 042001 (2014). [3] F. D. Cunden, F. Mezzadri, P. Vivo, J. Stat. Phys. 164, 1062 (2016). [4] B. Lacroix-A-Chez-Toine, A. Grabsch, S. N. Majumdar, G. Schehr, J. Stat. Mech.: Theory Exp. 013203 (2018).
    Close abstract

    Gravity, entanglement, and bit threads

    Date:
    09
    Thursday
    January
    2020
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Matthew Headrick
    Organizer: Faculty of Physics
    Details: 11:00 - Coffee, Tea and more
    Abstract: In trying to understand quantum gravity at a fundamental level, one of the most ... Read more In trying to understand quantum gravity at a fundamental level, one of the most confusing questions is where the degrees of freedom are. So-called holographic dualities help with this question, by showing that certain quantum gravity theories are equivalent to conventional quantum field theories, in which we understand in principle where the degrees of freedom are and how they interact. Using such dualities, a new way of understanding entanglement in quantum gravity, involving so-called “bit threads”, has recently been developed. From this point of view, space becomes a channel for carrying entanglement of fundamental degrees of freedom. We will explain what holographic dualities are, what bit threads are, and what they might tell us about the nature of space in quantum gravity.
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    Adaptation of bacteria with CRISPR and adaptation on a rugged fitness landscape

    Date:
    06
    Monday
    January
    2020
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Marija Vucelja
    Organizer: Department of Physics of Complex Systems
    Abstract: I will tell you two stories of adaptation of populations aided and enriched by s ... Read more I will tell you two stories of adaptation of populations aided and enriched by statistical physics approaches. The first story is about the adaptation of bacteria with CRISPR. CRISPR-Cas is a famous biology buzz word, due to its applications to gene editing. However, CRISPR-Cas is also a prokaryote immune system. It works as a “library” of previous infections. This library contains snippets of exogenous genetic material. With a new infection, the library is consulted, and if a match is found, the attempt will be made to neutralize the intruding genome. Bacteria use CRISPR-Cas as an immune system against phages and plasmids. Such immunity is hereditary and dynamic — it can be gained and lost during the lifetime of the single bacteria. Also, the process of acquiring snippets when exposed to the same phage is stochastic, and the same strain bacteria in a population contain different CRISPR loci content and thus variable immunity to the phage. We use dynamical systems approaches to predict the shape of this diverse distribution of CRISPR loci content within a bacterial population as a function of two crucial parameters — the rate of acquisition and the immunity to the phage. The second story is about adaptation on a rugged fitness landscape. A crude measure of adaption to a new environment called fitness. Often one defines fitness as the expected growth rate. The higher the fitness, the more thriving is a population. What happens over long times for a population with a finite genome — when all beneficial, fitness mutations, are exhausted? Contrary to expectations, the experiments show that fitness does not reach a plateau. Here we introduce a spin-glass microscopic model, where a genome can be represented as a spin configuration, and individual spins are genes. The fitness plays the role of minus the Hamiltonian of the system. We use numerical approaches and estimates to study hopping between metastable states on a rugged fitness landscape. We show that with gene interactions (interacting spins), double beneficial mutations (flipping of pairs of spins) can lead to a slow, logarithmic increase of fitness in a wide class of cases.
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    Adaptation of bacteria with CRISPR and adaptation on a rugged fitness landscape

    Date:
    06
    Monday
    January
    2020
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Marija Vucelja
    Organizer: Department of Physics of Complex Systems
    Abstract: I will tell you two stories of adaptation of populations aided and enriched by s ... Read more I will tell you two stories of adaptation of populations aided and enriched by statistical physics approaches. The first story is about the adaptation of bacteria with CRISPR. CRISPR-Cas is a famous biology buzz word, due to its applications to gene editing. However, CRISPR-Cas is also a prokaryote immune system. It works as a “library” of previous infections. This library contains snippets of exogenous genetic material. With a new infection, the library is consulted, and if a match is found, the attempt will be made to neutralize the intruding genome. Bacteria use CRISPR-Cas as an immune system against phages and plasmids. Such immunity is hereditary and dynamic — it can be gained and lost during the lifetime of the single bacteria. Also, the process of acquiring snippets when exposed to the same phage is stochastic, and the same strain bacteria in a population contain different CRISPR loci content and thus variable immunity to the phage. We use dynamical systems approaches to predict the shape of this diverse distribution of CRISPR loci content within a bacterial population as a function of two crucial parameters — the rate of acquisition and the immunity to the phage. The second story is about adaptation on a rugged fitness landscape. A crude measure of adaption to a new environment called fitness. Often one defines fitness as the expected growth rate. The higher the fitness, the more thriving is a population. What happens over long times for a population with a finite genome — when all beneficial, fitness mutations, are exhausted? Contrary to expectations, the experiments show that fitness does not reach a plateau. Here we introduce a spin-glass microscopic model, where a genome can be represented as a spin configuration, and individual spins are genes. The fitness plays the role of minus the Hamiltonian of the system. We use numerical approaches and estimates to study hopping between metastable states on a rugged fitness landscape. We show that with gene interactions (interacting spins), double beneficial mutations (flipping of pairs of spins) can lead to a slow, logarithmic increase of fitness in a wide class of cases.
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    Foundations of Computer Science Colloquium

    Date:
    06
    Monday
    January
    2020
    Lecture / Seminar
    Time: 11:15-12:45
    Title: Some Connections Between the Conjectures in Fine-Grained Complexity
    Location: Jacob Ziskind Building
    Lecturer: Dr. Amir Abboud
    Organizer: Department of Mathematics
    Details: Fine-grained complexity utilizes a small set of conjectures to derive conditiona ... Read more Fine-grained complexity utilizes a small set of conjectures to derive conditional lower bounds for a large collection of problems. These conjectures concern the time complexity of a few core problems such as k-SAT, Orthogonal Vectors, 3SUM, k-Clique, and Set Cover.
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    Abstract: Fine-grained complexity utilizes a small set of conjectures to derive condition ... Read more Fine-grained complexity utilizes a small set of conjectures to derive conditional lower bounds for a large collection of problems. These conjectures concern the time complexity of a few core problems such as k-SAT, Orthogonal Vectors, 3SUM, k-Clique, and Set Cover. The relationships between these conjectures are poorly understood. This talk will discuss some connections between the conjectures, including a tight reduction from Weighted-k-Clique to Orthogonal Vectors and new (quantum-inspired) findings about the Set Cover Conjecture.
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    Pulling Yourself by your Bootstraps in Quantum Field Theory

    Date:
    02
    Thursday
    January
    2020
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Leonardo Rastelli
    Organizer: Faculty of Physics
    Details: 11:00 - Coffee, Tea and more
    Abstract: Quantum field theory (QFT) is the universal language of theoretical physics, und ... Read more Quantum field theory (QFT) is the universal language of theoretical physics, underlying the Standard Model of elementary particles, the physics of the early Universe and a host of condensed matter phenomena such as phase transitions and superconductivity. A great achievement of 20th-century physics was the understanding of weakly coupled quantum field theories where interactions can be treated as small perturbations of otherwise freely moving particles. Critical challenges for the 21st century include solving the problem of strong coupling and mapping the whole space of consistent QFTs. In this lecture, I will overview the bootstrap approach, the idea that theory space can be determined from the general principles of symmetry and quantum mechanics. This strategy provides a new unifying language for QFT and has allowed researchers to make predictions for physical observables even in strongly coupled theories. By holographic duality, the bootstrap program has also implications for the space of consistent quantum gravity theories.
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    Physical Genomics Harnessing physics and chemistry for single-molecule analysis of the human genome

    Date:
    30
    Monday
    December
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Yuval Ebenstein, TAU
    Organizer: Department of Physics of Complex Systems
    Abstract: DNA is an amazing memory device that holds the operating system of life. However ... Read more DNA is an amazing memory device that holds the operating system of life. However, DNA sequencing fails to extract the full range of information associated with genetic material and is lacking in its ability to resolve variations between genomes. As a consequence, many genomic features remain poorly characterized in the human genome reference. In addition, the information content of the genome extends beyond the base sequence in the form of chemical modifications such as DNA methylation or DNA damage lesions that chemically encode our life experiences in our DNA. By applying experimental principles of single molecule detection we gain access to the structural variation and long range patterns of genetic and epigenetic information. We show how physical extension of long DNA molecules on surfaces and in nanofluidic channels reveals such information in the form of a linear, optical “barcode” showing distinct types of observables. Recent results from our lab demonstrate our ability to detect epigenetic marks and various forms of DNA damage on individual genomic DNA molecules and use this information for medical diagnostics.
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    The Large Synoptic Survey Telescope: Status Update and Prospects for Science

    Date:
    26
    Thursday
    December
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Steven M. Kahn
    Organizer: Faculty of Physics
    Details: 11:00 - Coffee, Tae and more
    Abstract: The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field groun ... Read more The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field ground-based telescope designed to provide a time-domain imaging survey of the entire southern hemisphere of sky in six optical colors (ugrizy). Over ten years, LSST will obtain ~ 1,000 exposures of every part of the southern sky, enabling a wide-variety of distinct scientific investigations, ranging from studies of small moving bodies in the solar system, to constraints on the structure and evolution of the Universe as a whole. The development of LSST is a collaboration between the US National Science Foundation, which is supporting the development of the telescope and data system, and the US Department of Energy, which is supporting the development of the 3.2 gigapixel camera, the largest digital camera ever fabricated for astronomy. Approved in 2014, LSST is now well into construction, and is on track to beginning operations in 2022. I will review the design and technical status of the Project, and provide an overview of some of the exciting science highlights that we expect to come from this facility.
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    New directions for diffusive processes: defect formation through a nonequilibrium phase transition, open quantum systems and uncertainty relations in mesoscopic systems

    Date:
    23
    Monday
    December
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Ohad Shpielberg
    Organizer: Department of Physics of Complex Systems
    Abstract: The macroscopic fluctuation theory gives an efficient hydrodynamic description f ... Read more The macroscopic fluctuation theory gives an efficient hydrodynamic description for classical nonequilibrium diffusive systems. In this talk, we would cover how it can be applied and generalised in three directions: a. Towards a theory for open quantum diffusive systems, comparable to the macroscopic fluctuation theory. b. Defect formation as a system is (slowly) driven in time through a continuous phase transition can be described by a scaling theory - the Kibble-Zurek Mechanism. The macroscopic fluctuation theory allows to explore the exact evolution of defects for a large set of cases. Thus, we are in a position to go beyond the scaling arguments of the Kibble-Zurek Mechanism. c. The recently discovered thermodynamic uncertainty relations define a transport efficiency in thermal systems showing that the mean current, current fluctuations and dissipation are intimately linked. Here we will briefly show how this idea can be extended to (athermal) mesoscopic coherent processes.
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    Chemical and Biological Physics Guest Seminar

    Date:
    19
    Thursday
    December
    2019
    Lecture / Seminar
    Time: 15:00
    Title: Quantum theory in practice
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Aharon Brodutch
    Organizer: Department of Chemical and Biological Physics
    Abstract: Quantum theory has been incredibly successful at explaining known phenomena and ... Read more Quantum theory has been incredibly successful at explaining known phenomena and making new predictions that have led to some of the most important scientific and technological breakthroughs in the past century. Quantum computers are arguably the boldest prediction of the theory, but the level of control required to build them is extremely challenging. The requirements for building universal fault tolerant quantum computers (i.e computers that can run any quantum algorithm with high accuracy) are far beyond current capabilities, but less powerful (intermediate) quantum machines are already available, with some accessible online. The minimal requirements for such intermediate machines to significantly outperform ordinary (classical) computers is currently an open area of research. One approach to study the capabilities of intermediate quantum machines, is to study how small subsystems become correlated (and entangled) during a computation. I will provide an overview of work in this direction with some surprising results on the possible role of quantum entanglement. These results provide new insights into quantum theory and quantum technology.
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    Overcoming resolution limits with quantum sensing by utilising error correction

    Date:
    19
    Thursday
    December
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Alex Ratzker
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: Quantum sensing and metrology exploit quantum aspects of individual and complex ... Read more Quantum sensing and metrology exploit quantum aspects of individual and complex systems to measure a physical quantity. Quantum sensing targets a broad spectrum of physical quantities, of both static and time-dependent types. While the most important characteristic for static quantities is sensitivity, for time-dependent signals it is the resolution, i.e. the ability to resolve two different frequencies. The decay time of the probe imposes a fundamental limit on the quantum sensing efficiency. While error correction methods can prolong this time it was not clear if such a procedure could be used in a quantum sensing protocol. In this talk I will present a study of spectral resolution problems with quantum sensors, and the development of a new super-resolution method that relies on quantum features for which the limitation imposed by the finite decay time can be partially overcome by error correction.
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    Learning the code of large neural populations using random nonlinear projections

    Date:
    16
    Monday
    December
    2019
    Lecture / Seminar
    Time: 14:15
    Lecturer: Elad Schneidman, Department of Neurobiology, WIS
    Organizer: Department of Physics of Complex Systems

    "A Stochastic approach to thermal density functional theory"

    Date:
    16
    Monday
    December
    2019
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Yael Cytter
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: abstract Warm dense matter (WDM) is state of matter characterized by temperatur ... Read more abstract Warm dense matter (WDM) is state of matter characterized by temperatures of the order of 10,000 K and nuclear densities of magnitude significantly higher than those found in ordinary condensed matter. WDM is found in many fields of physics, chemistry, planetary sciences, and even industry: stellar and planetary science, laser-induced chemical processes in solids and on surfaces as well as plasma physics. Nowadays, using intense lasers, WDM properties can be investigated in the laboratory, thus requiring attention to theoretical research for interpretation and understanding of the results. The theoretical description of the regime is complex, being the intermediate between condensed matter physics (i.e., quantum description) and plasma physics (classical thermodynamics). WDM is often described theoretically using finite-temperature Kohn-Sham (KS) density functional theory (DFT) calculations, with reasonably good agreement to experiments. These calculations in finite (non-zero) temperatures are costly due to the large number of fractionally occupied KS orbitals that are involved. The computational cost exhibits cubic scaling with temperature. Stochastic density functional theory (sDFT), developed recently [1,2,3] appears to be a viable approach to WDM since it is “orbital-free” and yet fully KS. The sDFT approach uses the Fermi Dirac occupation operator to calculate the energy, and finds the electronic density and other expectation values by executing the trace in a stochastic way using random orbitals; in doing so, it skips over the step of calculating the KS orbitals. We further use the stochastic trace formula to calculate the conductivity based on Kubo-Greenwood formula. In the talk, convergence of the free energy will be discussed, as well as calculations of equations of states and statistical convergence of the conductivity when calculated based on stochastic thermal DFT. Transition to metallization in he-h systems was seen in temperature of ~60kK using the stochastic approach. [1] R. Baer, D. Neuhauser, E. Rabani, Phys. Rev. Lett. 111, 106402 (2013) [2] Y. Cytter, E. Rabani, D. Neuhauser, and R. Baer Phys. Rev. B 97, 115207 (2018) [3] Yael Cytter, Eran Rabani, Daniel Neuhauser, Martin Preising, Ronald Redmer, and Roi Baer Phys. Rev. B 100, 195101 (2019)
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    In vivo multimodality imaging of immune-vascular interactions in cardiovascular disease

    Date:
    12
    Thursday
    December
    2019
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Katrien Vandoorne
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Cardiovascular disease is a result of genetic and environmental risk factors tha ... Read more Cardiovascular disease is a result of genetic and environmental risk factors that together generate arterial and cardiac pathologies. Blood vessels connect multiple organ systems throughout the entire body allowing organs to interact via circulating messengers. Multimodality imaging achieves integration of these interfacing systems’ distinct processes, quantifying interactions that contribute to cardiovascular disease. Noninvasive multimodality imaging techniques are emerging tools that can further our understanding of this complex and dynamic interplay. Multichannel multimodality imaging including optics, CT, PET and MRI, are particularly promising because they can simultaneously sample multiple biomarkers. As the opportunities provided by imaging expand, mapping interconnected systems will help us decipher the complexity of cardiovascular disease and monitor novel therapeutic strategies.
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    A quantitative footprint of irreversibility in the absence of observable currents

    Date:
    09
    Monday
    December
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Gili Bisker
    Organizer: Department of Physics of Complex Systems
    Abstract: Time irreversibility is the hallmark of nonequilibrium dissipative processes. De ... Read more Time irreversibility is the hallmark of nonequilibrium dissipative processes. Detecting dissipation is essential for our basic understanding of the underlying physical mechanism, however, it remains a challenge in the absence of observable directed motion, flows, or fluxes. Additional difficulty arises in complex systems where many internal degrees of freedom are inaccessible to an external observer. In living systems, for example, the dissipation is directly related to the hydrolysis of fuel molecules such as adenosine triphosphate (ATP), whose consumption rate is difficult to directly measure in many experimental setups. In this talk, I will introduce a novel approach to detect time irreversibility and estimate the entropy production from time-series measurements, even in the absence of observable currents. This method can be implemented in scenarios where only partial information is available and thus provides a new tool for studying nonequilibrium phenomena. 1. G. Bisker et al. Inferring broken detailed balance in the absence of observable currents, Nature Communications, 10(1), 1-10 (2019) 2. G. Bisker et al. Hierarchical Bounds on Entropy Production Inferred from Partial Information, Journal of Statistical Mechanics: Theory and Experiment (9), 093210 (2017)
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    What Processes Shape the Disks of Galaxies?

    Date:
    05
    Thursday
    December
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Hans-Walter Rix
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tae and more
    Abstract: The Milky Way, as a very average spiral galaxy, can serve as a galaxy model orga ... Read more The Milky Way, as a very average spiral galaxy, can serve as a galaxy model organism to tell us which physical processes shape the current structure and stellar content of galaxies: what sets the overall radial profile of the disk, which the present-day orbital of any star, and how much formation memory does the Milky Way's disk retain? We can now draw on global Galactic stellar surveys that constrain orbits, abundances and ages. I will show how modelling these data now shows that global radial orbit migration is a very strong effect that decisively shapes the structure of the Milky Way's disk. If the Milky Way is typical in this respect this explains why galaxy disk profiles are exponential. And I will also sketch how data from the Gaia mission can now tell us in far more detail the mechanisms that drive orbit evolution throughout our disk.
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    The Importance of Mechanistic Understanding for Developing Novel Umpolung Reactions and Solar Induced Processes

    Date:
    03
    Tuesday
    December
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Helen and Milton A. Kimmelman Building
    Lecturer: Prof. Alex M. Szpilman
    Organizer: Department of Molecular Chemistry and Materials Science

    Active Matter: `active thermodynamics’ and the dynamics of biopolymer gels

    Date:
    01
    Sunday
    December
    2019
    Lecture / Seminar
    Time: 13:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Tomer Markovich
    Organizer: Department of Physics of Complex Systems
    Abstract: Active materials are composed of many components that can convert energy from it ... Read more Active materials are composed of many components that can convert energy from its environment (usually in the form of chemical energy) into directed mechanical motion. Time reversal symmetry is thus locally broken, leading to a variety of novel phenomena such as motility induced phase separation, reversal of the Ostwald process and flocking. Examples of active matter are abundant and range from living matter such as bacteria, actomyosin networks and bird flocks to Janus particles, colloidal rollers and macroscale driven chiral rods. Nevertheless, in many cases experiments on active materials exhibit equilibrium like properties (e.g., sedimentation of bacteria). In the first part of the talk I will try to answer the important question: how do we know a system is `active’? And if it is, can we have generic observables as in equilibrium thermodynamics? Can we measure how far it is from equilibrium? In the second part of the talk I will focus on examples of activity in biopolymer gels, such as the cytoskeleton of living cells. I will show some of the effects of active motors with emphasis on chiral motors. The latter does not have a unique hydrodynamic description, which one can utilize to gain access to the microscopic details of the complex motors using macroscopic measurements. I will also discuss non-motor activity and demonstrate how it can result in contractility, e.g., in the process of cell division.
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    Quantum Many-Body Integrability, Solvability, and Chaos

    Date:
    21
    Thursday
    November
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Vladimir Rosenhaus
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: This talk is concerned with the question: How can we characterize, find, and sol ... Read more This talk is concerned with the question: How can we characterize, find, and solve quantum field theories and many-body systems that exhibit features of quantum chaos? We describe the recently discovered Sachdev-Ye-Kitaev model: a quantum mechanical system of a large number of fermions with all-to-all quartic, Gaussian-random, interactions that, remarkably, is chaotic, nearly conformally invariant, and solvable. We contrast this with integrable two-dimensional quantum field theories, such as the Sine-Gordon model. We end with some comments on hopes for a framework to find nearly integrable quantum field theories that are nearly solvable.
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    STATISTICAL DYNAMICS DAY XI

    Date:
    20
    Wednesday
    November
    2019
    Lecture / Seminar
    Time: 09:00-17:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Organizer: Department of Physics of Complex Systems
    Abstract: 09:40 – 10:00 Yoav Sagi - Technion “The attractive Fermi polaron problem - e ... Read more 09:40 – 10:00 Yoav Sagi - Technion “The attractive Fermi polaron problem - experimental study with an ultracold Fermi gas” 10:00 – 10:20 David Kessler – Bar-Ilan University “Quantum First-Detection Problems” 10:20 – 10:40 Dekel Shapira – Ben-Gurion University “Interplay of Quantum and stochastic transport along chains“ 10:40 – 11:00 Bertrand Lacroix – Weizmann Institute "Universal intermediate deviation functions for the 2d One Component Plasma” Coffee Break 11:30 – 11:50 Erez Braun - Technion “Is morphogenesis in animal development reversible?” 11:50 – 12:10 Yasmine Meroz – Tel-Aviv University “Form and Function: Emergent Structures in Growth-Driven Systems” 12:10 – 12:30 Ehud Meron – Ben-Gurion University “Dynamics of desertification fronts” 12:30 – 12:50 Iddo Eliazar – Tel-Aviv University “Max-Min/Min-Max of random matrices” Lunch 14:00 – 14:20 Ofer Biham – Hebrew University “Convergence of contracting networks towards an asymptotic maximum-entropy structure” 14:20 – 14:40 Asaf Miron – Weizmann Institute “Phase transition in transport though a narrow-channel” 14:40 – 15:00 Gianluca Teza – Weizmann Institute “Memory leaves entropy production fluctuations invariant under coarse-graining” Coffee Break 15:20 – 15:40 Hillel Aharoni – Weizmann Institute “Universal Inverse Design of Nematic Elastomer Surfaces”. 15:40 – 16:00 Michael Moshe – Hebrew University “Mechanical Meta-Materials as lattices of quadrupolar elastic charges” 16:00 – 16:20 Naomi Oppenheimer – Tel-Aviv University “Hurricane dynamics in a membrane"
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    Systematics of spectral shifts in random matrix ensembles

    Date:
    11
    Monday
    November
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Uzy Smilansky
    Organizer: Department of Physics of Complex Systems

    Kepler's Multiple Planet Systems

    Date:
    10
    Sunday
    November
    2019
    Lecture / Seminar
    Time: 14:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Jack Lissauer
    Organizer: Department of Earth and Planetary Sciences
    Abstract: More than one-third of the 4000+ planet candidates found by NASA’s Kepler spac ... Read more More than one-third of the 4000+ planet candidates found by NASA’s Kepler spacecraft are associated with target stars that have more than one planet candidate, and such “multis” account for the vast majority of candidates that have been verified as true planets. The large number of multis tells us that flat multiplanet systems like our Solar System are common. Virtually all of the candidate planetary systems are stable, as tested by numerical integrations that assume a physically motivated mass-radius relationship. Statistical studies performed on these candidate systems reveal a great deal about the architecture of planetary systems, including the typical spacing of orbits and flatness. The characteristics of several of the most interesting confirmed Kepler & TESS multi-planet systems will also be discussed.
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    A new attempt to solve the type Ia supernova problem

    Date:
    07
    Thursday
    November
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Boaz Katz
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: Supernovae distribute most of the chemical elements that we are made of and are ... Read more Supernovae distribute most of the chemical elements that we are made of and are detected daily, yet we still do not know how they explode. Type Ia supernovae consist of most recorded supernovae and are likely the result of thermonuclear explosions of white dwarfs (common compact stars with mass similar to the sun and radius similar to earth), but what mechanism causes about 1% of white dwarfs to ignite remains unknown. I will describe our ongoing recent attempt to solve this puzzle that involves a new potential answer - direct collisions of white dwarfs in multiple stellar systems, new robust tools to compare explosion models to observations - in particular the use of global conservation of energy in emitted radiation, and new key observations - in particular late-time spectra of ~100 recent supernovae.
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    Boron subphthalocyanines and subnaphthalocyanines for organic photovoltaics

    Date:
    06
    Wednesday
    November
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Tim Bender
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: For some time, our group has been focused on the design, synthesis and applicati ... Read more For some time, our group has been focused on the design, synthesis and application of derivatives of boron subphthalocyanines (BsubPcs), a macrocyclic molecule with chelated central boron atom. Our focal point has been and continues to be equally balanced between the basic and applied chemistry of BsubPcs, their application as light absorbing and electronic conducting materials in organic photovoltaics (OPVs)/solar cells. For this presentation I will outline how we have developed BsubPcs for their application in OPVs and other organic electronic devices. For OPVs, we have developed an approach to their development whereby their basic and applied chemistry is justified by a development cycle which includes their physical chemistry and characterization, their immediate integration into OPVs and based on their indoor stability are placed in the ambient environment to truly address their ultimate application in organic solar cells. Integrated into this cycle is a computational modeling methodology that is used to screen potential BsubPcs for their application in organic electronic devices including OPVs/organic solar cells. Most recently we have identified a pathway to BsubPcs whereby all carbons are bio-sourced and I will highlight how the computational model justified the time and resource commitment to their synthesis and development. In addition to BsubPcs, we have taken an equal approach to extended -conjugated derivatives of BsubPcs, boron subnaphthalocyanines (BsubNcs); BsubNcs being unique and beneficial materials for OPV application. We have shown that BsubNcs actually become randomly chlorinated during their synthetic preparation and actually then form a mixed alloy composition of chlorinated materials, which we have designated as Cl-ClnBsubNcs. The mixed alloy composition is unique, and has been determined to be a mixture of 24 (more or less) chlorinated BsubNcs despite being a mixture that uniquely forms single crystals. The formation of single crystals is enabled by the chlorine atoms occupying vacancies within the solid state structure, the vacancies being the so-called “bay position” of the BsubNcs structure. During this presentation I will highlight how odd the mixed alloy composition of organic materials is and how hard it has been to separate the mixed alloyed composition. I will also highlight how we are moving forward with purposefully making mixed alloyed compositions of our macrocyclic compounds BsubPcs and BsubNcs fully justified by the potential performance increase in organic solar cells. Co-authors/investigators will be identified during this presentation. #-- Some Relevant References. [1] “Outdoor Performance and Stability of Boron Subphthalocyanines Applied as Electron Acceptors in Fullerene-Free Organic Photovoltaics.” Josey, D.; et al, ACS Energy Lett., 2017, 2(3), 726–732. DOI: 10.1021/acsenergylett.6b00716. [2] “Boron Subphthalocyanines as Electron Donors in Outdoor Lifetime Monitored Organic Photovoltaic Cells.” Garner, R.K.; et al, Solar Energy Materials and Solar Cells, 2018 176, 331-335. DOI: 10.1016/j.solmat.2017.10.018 [3] “8.4% efficient fullerene-free organic solar cells exploiting long-range exciton energy transfer” Cnops, K.; et al., Nature Comm., 5, Article number: 3406, DOI:10.1038/ncomms4406. [4] “The mixed and alloyed chemical composition of chloro-(chloro)n-boron subnaphthalocyanines dictates their physical properties and performance in organic photovoltaics.” Dang, J.D.; et al, J. Mat. Chem. A., 2016, 4, 9566-9577. DOI: 10.1039/C6TA02457B [5] “Phenoxy-(chloro)n-boron subnaphthalocyanines; alloyed mixture, electron-accepting functionality, enhanced solubility for bulk heterojunction organic photovoltaics” Dang, J.D.; et al, ACS Omega, 2018, 3(2), 2093–2103. DOI: 10.1021/acsomega.7b01892. [6] “The Mixed Alloyed Chemical Composition of Chloro-(chloro)n-Boron Subnaphthalocyanines Dictates Their Performance as Electron-Donating and Hole-Transporting Materials in Organic Photovoltaics” Garner, R.K.; et al, ACS Appl. Energy Materials, 2017, 1(3), 1029-1036. DOI: 10.1021/acsaem.7b00180. [7] "Outdoor Stability of Chloro-(Chloro)n-Boron Subnaphthalocyanine and Chloro-Boron Subphthalocyanine as Electron Acceptors in Bilayer and Trilayer Organic Photovoltaics" Josey, D.; et al, ACS Applied Energy Materials, 2019, 2(2), 979–986. DOI:10.1021/acsaem.8b01918
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    Ocean Worlds of the Outer Solar System: Life as we know it or life as we don’t?

    Date:
    03
    Sunday
    November
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Alex Hayes
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Recent discoveries have shown that habitable environments likely exist in subsur ... Read more Recent discoveries have shown that habitable environments likely exist in subsurface water oceans within the outer planet moons of Europa and Enceladus. On Titan, the largest moon of Saturn, lakes and seas of liquid hydrocarbon exist in addition to a vast subsurface water ocean. These places represent ideal locations for hydrothermal environments that could sustain life as we know it and, in Titan’s case, perhaps even life as we don’t. The next generation of uncrewed planetary spacecraft will be designed to search for the signs of life in one or more of these worlds. This lecture will begin with a brief review of the discoveries that have motivated a renewed importance for Ocean World exploration, before diving into Titan's lakes and seas to discuss recent findings related to its hydrocarbon-based hydrologic cycle and setting the stage for the newly selected Dragonfly quadcopter set to explore Titan in the mid 2030s.
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    "New Directions for Electricity and Fuels from Sunlight

    Date:
    29
    Tuesday
    October
    2019
    Lecture / Seminar
    Time: 11:00-12:30
    Title: Prof.Israel Rubinstein Memorial Lecture
    Location: Gerhard M.J. Schmidt Lecture Hall
    Lecturer: Prof. Harry Atwater
    Organizer: Department of Molecular Chemistry and Materials Science
    Details:
    Abstract: The recent rapid, global growth of photovoltaics has moved scientific research f ... Read more The recent rapid, global growth of photovoltaics has moved scientific research frontiers for solar energy conversion towards new opportunities including i) ultrahigh efficiency photovoltaics (η > 30%) and ii) direct synthesis of energy-dense chemical fuels from sunlight, including hydrogen and products from reduction of carbon dioxide. I will illustrate several examples of how design of materials for light harvesting, charge transport and catalytic selectivity can enable advances in electricity and fuel synthesis. Photonic design has opened new directions for high efficiency photovoltaics and luminescent solar concentrators. Semiconductors coupled to water oxidation and reduction catalysts have enabled approaches to photoelectrochemical solar-to-hydrogen generation with >19% efficiency using artificial photosynthetic structures. Solar-driven reduction of carbon dioxide presents both an enormous opportunity and challenge because of the need for selectivity in generating useful multi-carbon products by multiple electron and multi-proton transfer steps. Present work and future directions in selective photocatalytic and photo-electrocatalytic materials for artificial photosynthesis aimed at catalytic reduction of carbon dioxide will be discussed.
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    What limits the performance of halide perovskite solar cells

    Date:
    24
    Thursday
    October
    2019
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Arava Zohar
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Halide Perovskites, HaPs, make up a group of semiconducting materials with excel ... Read more Halide Perovskites, HaPs, make up a group of semiconducting materials with excellent light absorption and good electrical charge transport properties, which is remarkable given their low-temperature solution preparation. In my Ph.D. research, I investigated fundamental optoelectronic properties of HaP semiconductors to elucidate dominant charge transport mechanisms, with emphasis on providing design tools for high-efficiency solar cells to help transform the renewable, solar energy landscape. I will show how I characterized Fermi level positions and studied the self-doping mechanism of different HaP materials by using a suite of in situ measurements. My main conclusion was that halide vacancy defects (surface, interface, or bulk) and electron sharing between oxygen and the HaP surface, drive Fermi level changes. The former had been postulated but not experimentally shown, until my work. By elucidating the electric field distribution and photovoltage losses I could show that Br-based HaP device efficiency is limited mainly by a (relatively) high defect density at the anode/semiconductor interface.
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    Solar Photovoltaics: Recent Progress & Future Potential

    Date:
    26
    Thursday
    September
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Martin Green
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: The last five years have seen major reductions in silicon solar module prices, w ... Read more The last five years have seen major reductions in silicon solar module prices, with these dropping at a compounded rate approaching 20%/year over this period, with even more dramatic reductions in bids for bulk electricity supply through Power Purchase Agreements, to values as low as US$16.88/MWh. On the technology front, there have been substantial improvements in module energy conversion efficiency through displacement of established cell technology by the UNSW-invented and -developed PERC cell, complemented by the introduction of multi-busbar, half-cell and shingled modules. The introduction of PERC cells also allows low-cost fabrication of bifacially responsive modules, set to further boost effective efficiencies. These developments position photovoltaics to make a major impact on global CO2 omissions. A recent international study describes a technological path to a zero-carbon future by 2050 by transformation across all major energy sectors including not only electricity, but also heat, transport and industrial processes. This transformation is driven primarily by solar, with 63TW capacity calculated as required globally by this date, complemented by 8TW of wind, in the process creating 35 million direct energy jobs.
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    Forecast Skill and the Impact of Equatorial Waves in Two Operational Weather Prediction Systems

    Date:
    18
    Wednesday
    September
    2019
    Lecture / Seminar
    Time: 11:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: George N. Kiladis
    Organizer: Department of Earth and Planetary Sciences
    Abstract: Equatorially trapped waves account for a large portion of the perturbations with ... Read more Equatorially trapped waves account for a large portion of the perturbations within the tropical atmosphere and ocean. In the atmosphere, these disturbances are coupled to convection and determine a significant amount of rainfall variability on synoptic to intraseasonal time scales. Numerical models used for both weather and climate forecasting universally still have great difficulty simulating these convectively coupled disturbances. We assess the quantitative precipitation forecasts (QPF) skill of NOAA's Global Forecast System (GFS) and the European Centre for Medium Range Weather Forecasting Integrated Forecast System (IFS) operational models used for short term forecasts out to 10 days. Forecast skill was assessed by comparison with virtually independent GPM and CMORPH satellite precipitation estimates. Skill was quantified using a variety of metrics including pattern correlations for various latitude bands, temporal correlation at individual grid points, and space-time spectra of forecast precipitation over the global tropics and extratropics. Results reveal that, in general, initial conditions are reasonably well estimated in both forecast systems, as indicated by relatively good scores for the 6-12 hour forecasts. Since precipitation estimates are not directly assimilated into these systems, this indicates that the initialization of dynamical and thermodynamical fields is able to produce a reasonable QPF field, at least for the larger scales. We present evidence that the specification of the mass circulation rather than the moisture field is the primary source of this initial skill. Model skill is substantially better overall in the extratropics, however, tropical QPF in both systems is not considered useful by typical metrics much beyond a few days. A portion of this lack of tropical skill in can be traced back to inadequate treatment of equatorial wave activity coupled to convection. It is also demonstrated that extratropical forecast skill is positively correlated to preceding tropical skill, strongly suggesting that improvements in the treatment of tropics will lead to improved extratropical forecasts on the weekly and longer timescale.
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    Special Physics Colloquium

    Date:
    18
    Thursday
    July
    2019
    Colloquium
    Time: 11:15-12:30
    Title: Laser-based coherent control of free electrons
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Dr. Osip Schwartz
    Organizer: Faculty of Physics
    Details: 11:00 Refreshments
    Abstract: Laser manipulation of quantum particles, such as atoms, ions, and molecules, und ... Read more Laser manipulation of quantum particles, such as atoms, ions, and molecules, underpins much of modern physics. Electrons, too, can be coherently controlled by light. In this work, we study electron-laser interaction in free space and find that the conventional description based on the effective (ponderomotive) potential requires significant modification. We demonstrate laser-based phase manipulation of the electron wave function by performing interferometric experiments in a transmission electron microscope (TEM) and capture TEM images of the light wave. We then utilize the laser-induced phase shift to realize a nearly ideal phase plate for Zernike phase contrast TEM, solving a long-standing problem and addressing the challenge of dose-efficient interrogation of radiation-sensitive specimens. The laser phase plate is widely expected to advance the TEM studies of protein structure and cell organization.
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    Folding and cutting for clean energy – Origami and kirigami approaches to improving solar cells

    Date:
    16
    Sunday
    June
    2019
    Lecture / Seminar
    Time: 13:00-14:00
    Title: SAERI - Sustainability and Energy Research Initiative
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Prof. Max Shtein
    Organizer: Feinberg Graduate School
    Details: Host: Prof. Ron Milo Light refreshments will be served at 12:40

    Neutrinos as the key to the universe as we know it

    Date:
    06
    Thursday
    June
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Yuval Grossman
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: There are three open questions in physics which seem unrelated: Why is there onl ... Read more There are three open questions in physics which seem unrelated: Why is there only matter around us? How neutrinos acquire their tiny masses? Why all particles in Nature have integer electric charges? It turns out that these open questions are related. In the talk I will explain these open questions, the connection between them, and describe the on-going theoretical and experimental efforts in understanding them.
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    Phosphorus-Element Bond-Forming Reactions

    Date:
    04
    Tuesday
    June
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Helen and Milton A. Kimmelman Building
    Lecturer: Prof. Christopher C. Cummins
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Reactive Intermediates & Group Transfer Reactions. We design and synthesize mol ... Read more Reactive Intermediates & Group Transfer Reactions. We design and synthesize molecular precursors that can be activated by a stimulus to release a small molecule of interest. The molecular precursors themselves are isolated as crystalline solids; they are typically soluble in common organic solvents and can be weighed out and used as needed. For example, the molecule P2A2 (A = anthracene or C14H10) is a molecular precursor to the diatomic molecule P2. Compounds having the formula RPA serve to transfer the phosphinidene (PR) group either as a freely diffusing species (R = NR’2, singlet phosphinidene) or else by inner sphere mechanisms (R = alkyl, triplet phosphinidene). Using the RPA reagents we are developing reactions analogous to cyclopropanation and aziridination for delivery of the PR group to olefins with the formation of three-membered P-containing rings, phosphiranes. Metaphosphates and Phosphorylating Methodology. Crystalline metaphosphate salts with lipophilic counter cations are useful starting materials applicable in polar organic media. “Metaphosphate” refers to the inorganic ion PO3(-) which, unlike its chemical cousin, nitrate, exists not as a monomeric species but rather as oligomeric rings: [(PO3)n]n-. These cyclic phosphates can be converted into electrophilic phosphorylating agents (a) by treatment with peptide coupling reagents, or (b) by conversion into their crystalline acid forms and subsequent dehydration. Such activated cyclic phosphates can be used directly for oligophosphorylation of C, N, and O nucleophiles. Phosphorylation of the Wittig reagent leads to a new phosphorus ylide with a cyclic phosphate as the C-substituent and a non-hydrolyzable P-C bond, allowing for conjugation of oligophosphate groups to a biomolecule of interest by aldehyde olefination. Sustainable Phosphorus Chemistry. The industrial “thermal process” by which the raw material phosphate rock is upgraded to white phosphorus is energy intensive and generates CO2. We seek alternative chemical routes to value-added P-chemicals from phosphate starting materials obtained either by the agricultural “wet process” or by phosphorus recovery and recycling from waste streams. Trichlorosilane is a high production volume chemical for its use in the manufacture of silicon for solar panels. We show that trichlorosilane is a reductant for phosphate raw materials leading to the bis(trichlorosilyl) phosphide anion [P(SiCl3)2]- as a versatile intermediate en route to compounds containing P-C bonds.
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    Molecular electronic materials for solar energy conversion: understanding structure-function relationships

    Date:
    02
    Sunday
    June
    2019
    Lecture / Seminar
    Time: 13:00-14:00
    Title: SAERI - Sustainability and Energy Research Initiative
    Location: Nella and Leon Benoziyo Building for Biological Sciences
    Lecturer: Prof. Jenny Nelson
    Organizer: Feinberg Graduate School
    Details: Host: Prof. Ron Milo Light refreshments will be served at 12:40

    Imaging the human brain: ultra-high field MRI and new biomarkers

    Date:
    26
    Sunday
    May
    2019
    Lecture / Seminar
    Time: 13:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Rita Schmidt
    Organizer: Department of Physics of Complex Systems
    Abstract: Times New Roman (Headings CS) ... Read more Times New Roman (Headings CS)
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    Mixing and Unmixing in Planets

    Date:
    26
    Sunday
    May
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: David Stevenson
    Organizer: Department of Earth and Planetary Sciences

    Foundations of Computer Science Seminar

    Date:
    20
    Monday
    May
    2019
    Lecture / Seminar
    Time: 14:30-16:00
    Title: Gentle Measurement of Quantum States and Differential Privacy
    Location: Jacob Ziskind Building
    Lecturer: Guy Rothblum
    Organizer: Faculty of Mathematics and Computer Science,Department of Computer Science and Applied Mathematics,Department of Mathematics
    Details: We prove a new connection between gentle measurement (where one wants to measure ... Read more We prove a new connection between gentle measurement (where one wants to measure n quantum states, in a way that damages the states only by a little) and differential privacy (where one wants to query a database about n users, in a way that reveals only a little about any individual user). The connection is bidirectional, though with loss of parameters in going from DP to gentle measurement. Exploiting this connection, we present a new algorithm for approximating the outcomes of many measurements on a collection of quantum states, a task called "shadow tomography". The new algorithm has the advantages of being gentle and online (the measurements can be chosen adaptively). Joint work with Scott Aaronson. No prior knowledge about quantum mechanics or computing will be assumed.
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    Introduction to the quantum first detection problem

    Date:
    20
    Monday
    May
    2019
    Lecture / Seminar
    Time: 13:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Eli Barkai
    Organizer: Department of Physics of Complex Systems
    Abstract: We consider quantum dynamics on a graph, with repeated strong measurements perfo ... Read more We consider quantum dynamics on a graph, with repeated strong measurements performed locally at a fixed time interval τ. For example, a particle starting on node x and measurements performed on another node x'. From the basic postulates of quantum mechanics the string of measurements yields a sequence: no, no, no, … and finally in the n-th attempt a yes, i.e. the particle is detected. Statistics of the first detection time nτ are investigated, and compared with the corresponding classical first passage problem. Dark states, Zeno physics, a quantum renewal equation, winding number for the first return problem (work of A. Grunbaum et al.), total detection probability, detection time operators and time wave functions are discussed. References [1] H. Friedman, D. Kessler, and E. Barkai Quantum walks: the first detected passage time problem Phys. Rev. E. 95, 032141 (2017). Editor's suggestion. [2] F. Thiel, E. Barkai, and D. A. Kessler First detected arrival of a quantum walker on an infinite line Phys. Rev. Lett. 120, 040502 (2018).
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    A New Spin On Superconductivity

    Date:
    16
    Thursday
    May
    2019
    Colloquium
    Time: 11:15-12:30
    Title: PHYSICS MEMORIAL COLLOQUIUM IN HONOR OF PROF. YOSEPH IMRY
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Amir Yacoby
    Organizer: Faculty of Physics
    Details: 11:00 Coffee , tea and more
    Abstract: Mesoscopic physics, pioneered by Joe Imry nearly 4 decades ago, explores the beh ... Read more Mesoscopic physics, pioneered by Joe Imry nearly 4 decades ago, explores the behavior of matter on length scales where dimensionality, coherence, and interactions compete to produce material properties that are fundamentally different from their bulk counterparts. For example, the conventional wisdom of superconductivity, developed in 1957 by Bardeen, Cooper and Schrieffer (BCS) describes this state in terms of a condensate of electron pairs arranged in a spatially isotropic wave function with no net momentum or angular momentum (a spin-singlet configuration). However, on mesoscopic length scales entirely different types of superconductivity may be realized such as unconventional pairing where electrons are arranged in triplet rather than singlet configurations. Such superconductors may enable dissipationless transport of spin and may also give rise to elementary excitations that do not obey the conventional Fermi or Bose statistics but rather have non-Abelian statistics where the exchange of two particles transforms the state of the system into a new quantum mechanical state. In this talk I will describe some of our recent work that explores the proximity effect between a conventional superconductor and a semiconductor with strong spin-orbit interaction. Using supercurrent interference, we show that we can tune the induced superconductivity continuously from conventional to unconventional, that is from singlet to triplet. Our results open up new possibilities for exploring unconventional superconductivity as well as provide an exciting new pathway for exploring non-Abelian excitation.
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    Excitons in Flatland: Exploring and Manipulating Many-body Effects on the Optical Excitations in Quasi-2D Materials

    Date:
    01
    Wednesday
    May
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Diana Qiu
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Since the isolation of graphene in 2004, atomically-thin quasi-two-dimensional ( ... Read more Since the isolation of graphene in 2004, atomically-thin quasi-two-dimensional (quasi-2D) materials have proven to be an exciting platform for both applications in novel devices and exploring fundamental phenomena arising in low dimensions. This interesting low-dimensional behavior is a consequence of the combined effects of quantum confinement and stronger electron-electron correlations due to reduced screening. In this talk, I will discuss how the optical excitations (excitons) in quasi-2D materials, such as monolayer transition metal dichalcogenides and few-layer black phosphorus, differ from typical bulk materials. In particular, quasi-2D materials are host to a wide-variety of strongly-bound excitons with unusual excitation spectra and massless dispersion. The presence of these excitons can greatly enhance both linear and nonlinear response compared to bulk materials, making them ideal candidates for optoelectronics and energy applications. Moreover, due to enhanced correlations and environmental sensitivity, the electronic and optical properties of these materials can be easily tuned. I will discuss how substrate engineering, stacking of different layers, and the introduction or removal of defects can be used to tune the band gaps and optical selection rules in quasi-2D materials.
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    High Resolution Astronomy with Infrared Interferometry

    Date:
    01
    Wednesday
    May
    2019
    Colloquium
    Time: 00:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Dr. Reinhard Genzel
    Organizer: Faculty of Physics
    Details: 11:00 Coffee, Tea and more
    Abstract: The Center of our Galaxy is a unique laboratory for exploring the astrophysics a ... Read more The Center of our Galaxy is a unique laboratory for exploring the astrophysics around a massive black hole and testing General Relativity in this extreme environment. I will discuss the results of a major campaign of observing the Galactic Center in 2017/2018 with three instruments at the European Southern Observatory's VLT, including the novel GRAVITY interferometric beam combiner of the four 8-meter telescopes. During this period the B-star S2 completed a peri-passage at ~1400 Schwarzschild radii around the compact radio source SgrA*, and permitted for the first time a test of the equivalence principle and the detection of the first post-Newtonian orbital elements in a classical 'clock experiment' around a massive black hole. During bright states (
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    Period doubling as an early warning signal for desertification

    Date:
    29
    Monday
    April
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Omer Tzuk
    Organizer: Department of Physics of Complex Systems
    Abstract: The predictions for a warmer and drier climate and for increased likelihood of c ... Read more The predictions for a warmer and drier climate and for increased likelihood of climate extremes raise high concerns about the possible collapse of dryland ecosystems, and about the formation of new drylands where native species are less tolerant to water stress. Using a dryland-vegetation model for plant species that display different tradeoffs between fast growth and tolerance to droughts, we find that ecosystems subjected to strong seasonal variability, typical for drylands, exhibit a period-doubling route to chaos that results in early collapse to bare soil. We further find that fast-growing plants go through period doubling sooner and span wider chaotic ranges than stress-tolerant plants. We propose the detection of period-doubling signatures in power spectra as early indicators of ecosystem collapse that outperform existing indicators in their ability to warn against climate extremes and capture the heightened vulnerability of newly-formed drylands.
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    The dark Universe studied from deep underground: Exploring the low-mass frontier

    Date:
    18
    Thursday
    April
    2019
    Colloquium
    Time: 11:15-12:30
    Title: Physics Colloquium
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Federica Petricca
    Organizer: Faculty of Physics
    Details: 11:00 – coffee, tea, and more
    Abstract: Today, many observations on various astronomical scales provide compelling evide ... Read more Today, many observations on various astronomical scales provide compelling evidence for the existence of dark matter. Its underlying nature, however, remains an open question of present-day physics. The CRESST experiment is a direct dark matter search which aims to measure interactions of potential dark matter particles in an earth-bound detector, using scintillating CaWO4 crystals as target material operated as cryogenic calorimeters at millikelvin temperatures. Each interaction in CaWO4 produces a phonon signal in the target crystal and also a light signal that is measured by a secondary cryogenic calorimeter. This technology is particularly sensitive to small energy deposits induced by light dark matter particles, allowing the experiment to probe the low-mass region of the parameter space for spin-independent dark matter-nucleon scattering with high sensitivity. Results obtained in the first run of CRESST-III with a detector achieving a nuclear recoil threshold of 30.1 eV, probing dark matter particle masses down to 0.16 GeV/c2, will be presented.
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    Growth dynamics and complexity of national economies in the

    Date:
    15
    Monday
    April
    2019
    Lecture / Seminar
    Time: 14:15
    Title: Growth dynamics and complexity of national economies in the global trade network
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: A.L. Stella
    Organizer: Department of Physics of Complex Systems
    Abstract: Methods of statistical physics allow to explore the quantitative nexus among eco ... Read more Methods of statistical physics allow to explore the quantitative nexus among economic growth of a country, diversity of its productions, and evolution in time of its export basket(*). A stochastic model of evolution, calibrated on data for 1238 exports from 223 countries in 21 years, enables counterfactual analyses based on estimates of the part of growth due to resource transfers between different productions. Original use of the Boltzmann-Shannon entropy function leads to the construction of consistent measures of the efficiency of national economies and of the specialization of productions. Comparisons with dynamical and GDP pc data lead to clear distinctions among developed, developing, underdeveloped and risky countries. Perspective applications of the entropic measures in other fields (ecology, microbiology,..) where diversity has to be estimated from bipartite networks will be shortly outlined. (Work in collaboration with G. Teza, University of Padova, and M. Caraglio, Katholieke Universiteit Leuven.)
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    Prof. Barak Dayan - The second Quantum revolution: How the strangest effect in nature gives rise to new technologies

    Date:
    11
    Thursday
    April
    2019
    Lecture / Seminar
    Time: 12:00
    Title: The second Quantum revolution: How the strangest effect in nature gives rise to new technologies
    Location: Dolfi and Lola Ebner Auditorium
    Lecturer: Prof. Barak Dayan
    Organizer: Communications and Spokesperson Department
    Details: The lecture is in Hebrew

    Cut along dotted line: kirigami materials and device applications

    Date:
    10
    Wednesday
    April
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Max Shtein
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Simple 2-dimensional cut and fold patterns can be transformed into 3-dimensional ... Read more Simple 2-dimensional cut and fold patterns can be transformed into 3-dimensional shapes upon stretch-ing. We use this simple approach to develop mechanical metamaterials with several interesting proper-ties and applications. I will describe ways of tuning properties via geometric structure, and discuss ex-amples of how this can be used to achieve superior performance in mechanics, photonics, electronics, sensors, and other areas. References: “Dynamic kirigami structures for integrated solar tracking.” Nature Comm. 6, 8092 (2015) “A kirigami approach to engineering elasticity in nanocomposites through patterned defects.” Na-ture Mater., 14 (2015) 785 “An Electric Eel-Inspired Artificial Soft Power Source from Stacked Hydrogels.” Nature, 552 (2017) 214
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    Emergence and stability of a Brownian motor

    Date:
    08
    Monday
    April
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Alex Feigel
    Organizer: Department of Physics of Complex Systems
    Abstract: A Brownian motor rectifies thermal noise and creates useful work. Here we addres ... Read more A Brownian motor rectifies thermal noise and creates useful work. Here we address how this machine can emerge without predefined energy minimum in a system out of thermal equilibrium. Intuitively, Brownian motor as any artificial or biological machine should degrade with time. I will show that on contrary, a system with multiple degrees of freedom out of thermal equilibrium can be stable at a state that generates useful work. It is demonstrated with the help of ab initio analysis of a modified Feynman-Smoluchowski ratchet with two degrees of freedom. Out of thermal equilibrium, an environment imposes effective mechanical forces on nano-fabricated devices as well as on microscopic chemical or biological systems. Thus out of thermal equilibrium environment can enforce a specific steady state on the system by creating effective potentials in otherwise homogeneous configuration space. I present an ab initio path from the elastic scattering of a single gas particle by a mechanical system to the transition rate probability between the states of the system with multiple degrees of freedom, together with the corresponding Masters-Boltzmann equation and the average velocities of the system’s degrees of freedom as functions of the macroscopic parameters of the out-of-equilibrium environment. It results in Onsager relations that include the influence of the different degrees of freedom on each other. An interesting finding is that some of these forces persist even in a single temperature environment if the thermodynamic limit does not hold. In addition, the spatial asymmetry of the system’s stable state, together with the corresponding directed motion, may possess preferred chiral symmetry.
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    Quantum photonics for a new level of computer security and enhanced quantum computer architectures

    Date:
    04
    Thursday
    April
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Philip Walter
    Organizer: Faculty of Physics
    Abstract: The precise quantum control of single photons, together with the intrinsic advan ... Read more The precise quantum control of single photons, together with the intrinsic advantage of being mobile make optical quantum system ideally suited for delegated quantum information tasks, reaching from well-established quantum cryptography to quantum clouds and quantum computer networks. Here I present that the exploit of quantum photonics allows for a variety of quantum-enhanced data security for quantum and classical computers. The latter is based on feasible hybrid classical-quantum technology, which shows promising new applications of readily available quantum photonics technology for complex data processing. At the end I will also show how optical quantum computers allow for novel architectures that rely on superimposed order of quantum gates. As outlook I will discuss technological challenges for the scale up of photonic quantum computers, and our group’s current work for addressing some of those.
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    Optics in the Air

    Date:
    03
    Wednesday
    April
    2019
    Lecture / Seminar
    Time: 14:00
    Location: Sussman Family Building for Environmental Sciences
    Lecturer: Joseph Shaw
    Organizer: Department of Earth and Planetary Sciences
    Abstract: This talk will use photographs and diagrams to illustrate and explain some of th ... Read more This talk will use photographs and diagrams to illustrate and explain some of the beautiful optical phenomena observable in nature, such as ice‐crystal halos, rainbows, and sky colors, and will relate them to ongoing research into the spectral and spatial distribution of polarization in the atmosphere. Our group at Montana State University has pioneered all‐sky imaging methods to study skylight polarization and relate it to properties of airborne particles, clouds, and the underlying surface. Brief results from a deployment of all‐sky polarization imagers at the August 2017 solar eclipse will be shown and related to a more general discussion of atmospheric optical effects that can be seen by eye. The talk takes its title from my 2017 book, which describes optical phenomena in nature, especially as seen through airplane windows.
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    Imaging phase transitions with scanning SQUID

    Date:
    01
    Monday
    April
    2019
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Beena Kalisky
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: We use a local magnetic imaging technique, scanning SQUID microscopy, to map t ... Read more We use a local magnetic imaging technique, scanning SQUID microscopy, to map the spatial distribution of electronic states near surfaces and interfaces. We track conductivity, superconductivity and magnetism in systems undergoing phase transitions, where the local picture is particularly meaningful. I will describe two measurements: At the superconductor-insulator transition in NbTiN we map superconducting fluctuations and detect a non-trivial behavior near the quantum critical point. Near the metal to insulator transition at the 2D LaAlO3/SrTiO3 interface, we find that the conduction landscape changes dramatically and identify the way different types of defects control the behavior.
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    What makes a good solar cell?

    Date:
    31
    Sunday
    March
    2019
    Lecture / Seminar
    Time: 14:00-15:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Thomas Kirchartz
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: For the purpose of identifying novel absorber materials based on experimental or ... Read more For the purpose of identifying novel absorber materials based on experimental or computational material screening, it is useful to identify the basic ingredients required to make a good solar cell out of the combination of different absorber and contact materials. Figures of merit are needed that quantify whether a certain material is likely to perform well as a solar cell. To answer the question, which parameters are most important, we look into the key properties of good solar cells such as high absorption coefficient, mobility and charge carrier lifetime and study their interdependences and how they determine the efficiency at different thickness of the solar cell. Finally, we study some microscopic parameters such as the effective mass or electron-phonon coupling in a device to identify key microscopic properties that are likely to lead to a combination of high absorption, high mobilities and long lifetimes and thereby high photovoltaic efficiencies
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    Geometry, defects and motion in active matter

    Date:
    31
    Sunday
    March
    2019
    Lecture / Seminar
    Time: 13:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Luca Giomi
    Organizer: Department of Physics of Complex Systems
    Abstract: The paradigm of “active matter” has had notable successes over the past deca ... Read more The paradigm of “active matter” has had notable successes over the past decade in describing self-organization in a surprisingly broad class of biological and bio-inspired systems: from flocks of starlings to robots, down to bacterial colonies, motile colloids and the cell cytoskeleton. Active systems are generic non-equilibrium assemblies of anisotropic components that are able to convert stored or ambient energy into motion. In this talk, I will discuss some recent theoretical and experimental work on active nematic liquid crystals confined on two-dimensional curved interfaces and highlight how the geometrical and topological structure of the environment can substantially affect collective motion in active materials, leading to spectacular life-like functionalities.
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    Towards a Periodic Table Topological Materials

    Date:
    28
    Thursday
    March
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Andrei bernevig
    Organizer: Faculty of Physics
    Details: 11:00 – coffee, tea, and more
    Abstract: In the past few years the field of topological materials has uncovered many mate ... Read more In the past few years the field of topological materials has uncovered many materials which have topological bands: bands which cannot be continuable to a trivial, “atomic” limit, and which are characterized by an integer topological index. We will review the progress in the field and the new types of topological behavior that is expected from the many predictions in the field. We will also show how, using a new theory called Topological Quantum Chemistry, thousands of new topological materials can be predicted, classified and discovered. The result is that- so far - out of 30000 materials investigated - at least 30 percent of all materials in nature can be classified as topological. One ultimately aims for a full classification of topological materials, available on database websites such as www.topologicalquantumchemistry.com
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    Mathematical Analysis and Applications Seminar

    Date:
    26
    Tuesday
    March
    2019
    Lecture / Seminar
    Time: 11:15-12:30
    Title: Prediction of random and chaotic dynamics in nonlinear optics
    Location: Jacob Ziskind Building
    Lecturer: Amir Sagiv
    Organizer: Faculty of Mathematics and Computer Science,Department of Computer Science and Applied Mathematics,Department of Mathematics
    Details: The prediction of interactions between nonlinear laser beams is a longstanding o ... Read more The prediction of interactions between nonlinear laser beams is a longstanding open problem. A traditional assumption is that these interactions are deterministic. We have shown, however, that in the nonlinear Schrodinger equation (NLS) model of laser propagation, beams lose their initial phase information in the presence of input noise. Thus, the interactions between beams become unpredictable as well. Not all is lost, however. The statistics of many interactions are predictable by a universal model. Computationally, the universal model is efficiently solved using a novel spline-based stochastic computational method. Our algorithm efficiently estimates probability density functions (PDF) that result from differential equations with random input. This is a new and general problem in numerical uncertainty-quantification (UQ), which leads to surprising results and analysis at the intersection of probability and approximation theory.
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    Hyperuniformity of driven suspensions

    Date:
    25
    Monday
    March
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Haim Diamant
    Organizer: Department of Physics of Complex Systems
    Abstract: An arrangement of particles is said to be "hyperuniform" if its density fluctuat ... Read more An arrangement of particles is said to be "hyperuniform" if its density fluctuations over large distances are strongly suppressed relative to a random configuration. Crystals, for example, are hyperuniform. Recently, several disordered materials have been found to be hyperuniform. Examples are sheared suspensions and emulsions, and, possibly, random close packings of particles. We show that externally driven particles in a liquid suspension (as in sedimentation, for example) self-organize hyperuniformly in certain directions relative to the external force. This dynamic hyperuniformity arises from the long-range coupling, induced by the force and carried by the fluid, between the concentration of particles and their velocity field. We obtain the general requirements, which the coupling should satisfy in order for this phenomenon to occur. Under other conditions (e.g., for certain particle shapes), the coupling can lead to the opposite effect -- enhancement of density fluctuations and instability. We confirm these analytical results in a simple two-dimensional simulation.
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    Effects of Stochasticity and non-locality on a model of aggregation-fragmentation for Saturn rings

    Date:
    18
    Monday
    March
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Bijoy Daga
    Organizer: Department of Physics of Complex Systems
    Abstract: Saturn rings are composed of water-ice particles and traces of rocky materials w ... Read more Saturn rings are composed of water-ice particles and traces of rocky materials whose sizes may vary from micro meters to a few meters. A model that describes the observed size distribution considers aggregation and fragmentation of ring particles upon collision and the distribution can be calculated analytically by solving the steady state Smoluchowski equation. In writing down the deterministic Smoluchowski equation, it is assumed that the total mass is infinite. We try to understand the behavior of the system when the total mass is finite and the effects of Stochasticity becomes important. Further, it has been observed that the steady state in these systems becomes unstable and shows oscillations for non-local reaction Kernels. We will also discuss the role of non-locality for the case of finite total mass when Stochasticity becomes relevant and see whether oscillations would survive or not.
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    Phase separation in multicomponent liquid mixtures

    Date:
    17
    Sunday
    March
    2019
    Lecture / Seminar
    Time: 13:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Andrej Kosmrlj
    Organizer: Department of Physics of Complex Systems
    Abstract: Multicomponent systems are ubiquitous in nature and industry. While the physics ... Read more Multicomponent systems are ubiquitous in nature and industry. While the physics of binary and ternary liquid mixtures is well-understood, the thermodynamic and kinetic properties of N-component mixtures with N>3 have remained relatively unexplored. Inspired by recent examples of intracellular phase separation, we investigate equilibrium phase behavior and morphology of N-component liquid mixtures within the Flory-Huggins theory of regular solutions. In order to determine the number of coexisting phases and their compositions, we developed a new algorithm for constructing complete phase diagrams, based on numerical convexification of the discretized free energy landscape. Together with a Cahn-Hilliard approach for kinetics, we employ this method to study mixtures with N=4 and 5 components. In this talk I will discuss both the coarsening behavior of such systems, as well as the resulting morphologies in 3D. I will also mention how the number of coexisting phases and their compositions can be extracted with Principal Component Analysis (PCA) and K-Means clustering algorithms. Finally, I will discuss how one can reverse engineer the interaction parameters and volume fractions of components in order to achieve a range of desired packing structures, such as nested "Russian dolls" and encapsulated Janus droplets.
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    Nonlinear light-matter interaction: from superconducting qubits to spins in diamond

    Date:
    14
    Thursday
    March
    2019
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Eyal Buks
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: The talk is devoted to the study of the light-matter interaction in the nonlin ... Read more The talk is devoted to the study of the light-matter interaction in the nonlinear regime using three different cavity quantum electrodynamics (CQED) systems. The matter under study is a Josephson flux qubit in the first experiment [1], a spin ensemble of diphenylpicrylhydrazyl (DPPH) molecules in the second one, and different spin ensembles in a diamond lattice in the third one [3]. In all three experiments the matter under study interact with photons (light) confined in a superconducting microwave resonator (cavity). A variety of nonlinear effects are explored, including super-harmonic resonances, multi-photon resonances, effective cavity heating and cooling and motional narrowing induced by quantum-jumps. The effect of nonlinearity on spin detection sensitivity will be discussed. 1. Eyal Buks, Chunqing Deng, Jean-Luc F.X. Orgazzi, Martin Otto and Adrian Lupascu, Phys. Rev. A 94, 033807 (2016). 2. Hui Wang, Sergei Masis, Roei Levi, Oleg Shtempluk and Eyal Buks, Phys. Rev. A 95, 053853 (2017). 3. Nir Alfasi, Sergei Masis, Roni Winik, Demitry Farfurnik, Oleg Shtempluck, Nir Bar-Gill and Eyal Buks, Phys. Rev. A 97 (2018).
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    The Lab on a Beam: From Learning Physics to Atomic Manipulation in Scanning Transmission Electron Microscopy

    Date:
    13
    Wednesday
    March
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Sergei Kalinin
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Atomically-resolved imaging of materials has become the mainstay of modern mater ... Read more Atomically-resolved imaging of materials has become the mainstay of modern materials science, as enabled by advent of aberration corrected scanning transmission electron microscopy (STEM). However, the wealth of quantitative information contained in the fine details of atomic structure or spectra remains largely unexplored. In this talk, I will present the new opportunities enabled by physics-informed big data and machine learning technologies to extract physical information from static and dynamic STEM images. The deep learning models trained on theoretically simulated images or labeled library data demonstrate extremely high efficiency in extracting atomic coordinates and trajectories, converting massive volumes of statistical and dynamic data into structural descriptors. I further present a method to take advantage of atomic-scale observations of chemical and structural fluctuations and use them to build a generative model (including near-neighbor interactions) that can be used to predict the phase diagram of the system in a finite temperature and composition space. Similar approach is applied to probe the kinetics of solid-state reactions on a single defect level and defect formation in solids via atomic-scale observations. Finally, synergy of deep learning image analytics and real-time feedback further allows harnessing beam-induced atomic and bond dynamics to enable direct atom-by-atom fabrication. Examples of direct atomic motion over mesoscopic distances, engineered doping at selected lattice site, and assembly of multiatomic structures will be demonstrated. These advances position STEM towards transition from purely imaging tool for atomic-scale laboratory of electronic, phonon, and quantum phenomena in atomically-engineered structures.
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    The European Extremely Large Telescope

    Date:
    07
    Thursday
    March
    2019
    Colloquium
    Time: 11:15-12:30
    Title: Physics Colloquium
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Jason Spyromilio
    Organizer: Faculty of Physics
    Details: 11:00 – coffee, tea, and more
    Abstract: The European Southern Observatory is constructing a 39-m optical infrared telesc ... Read more The European Southern Observatory is constructing a 39-m optical infrared telescope. This 1.2 Billion Euro project when completed in 2024 will be the largest telescope ever built with unprecedented collecting area and with Adaptive Optics incorporated diffraction limited operations are the baseline. The design and challenges of the project shall be described. Some aspects of the diverse science cases shall be presented as will the current technical status.
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    I-CORE final meeting -The end of the quantum universe

    Date:
    03
    Sunday
    March
    2019
    Conference
    Time: 08:00-16:00
    Location: David Lopatie Conference Centre

    Publishing in Nature Communications

    Date:
    28
    Thursday
    February
    2019
    Lecture / Seminar
    Time: 10:00-11:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Bo Liu
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: In this talk, I will introduce the Nature Communications journal, the editorial ... Read more In this talk, I will introduce the Nature Communications journal, the editorial office in Shanghai, the editorial process and insiders’ view on the Nature Communications. Bo joined Nature Communications in March 2017. Following his undergraduate studies in Zhejiang University, China, he obtained his PhD in Physics at National University of Singapore. He then carried out his postdoctoral research at Graphene Research Center in Singapore and University of Washington. He currently handles manuscripts on solar cells and halide perovskite photophysics. Bo is based in the Shanghai office.
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    Diamond quantum technologies: magnetic sensing, hyperpolarization and noise spectroscopy

    Date:
    27
    Wednesday
    February
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Nir Bar-Gill
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Nitrogen Vacancy (NV) centers in diamond have emerged over the past few years as ... Read more Nitrogen Vacancy (NV) centers in diamond have emerged over the past few years as well-controlled quantum systems, with promising applications ranging from quantum information science to magnetic sensing. In this talk, I will first introduce the NV center system and the experimental methods used for measuring them and controlling their quantum spin dynamics. I will mention the application of magnetic sensing using NVs through the realization of a magnetic microscope [1]. I will then describe our work on nuclear hyperpolarization, potentially relevant for enhanced MRI contrast, and research into open quantum systems and quantum thermodynamics [2]. Finally, I will present related control sequences, which can be used to perform optimized quantum noise spectroscopy, allowing for precise characterization of the environment surrounding a quantum sensor [3]. 1. E. FARCHI ET. AL., SPIN 7, 1740015 (2017). 2. HOVAV, Y., NAYDENOV, B., JELEZKO, F. AND BAR-GILL, N., PHYS. REV. LETT. 120, 6, 060405 (2018) 3. Y. ROMACH ET. AL., PHYS. REV. APPLIED 11, 014064 (2019).
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    Chemical and Biological Physics and Organic Chemistry Seminar

    Date:
    26
    Tuesday
    February
    2019
    Lecture / Seminar
    Time: 11:00-12:00
    Title: The Dynamics of Charged Excitons in Electronically and Morphologically Homogeneous Single-Walled Carbon Nanotubes
    Location: Helen and Milton A. Kimmelman Building
    Lecturer: Prof Michael J. Therien
    Organizer: Department of Chemical and Biological Physics
    Abstract: The trion, a three-body charge-exciton bound state, offers unique opportunities ... Read more The trion, a three-body charge-exciton bound state, offers unique opportunities to simultaneously manipulate charge, spin and excitation in one-dimensional single-walled carbon nanotubes (SWNTs) at room temperature. Effective exploitation of trion quasiparticles requires fundamental insight into their creation and decay dynamics. Such knowledge, however, remains elusive for SWNT trion states, due to the electronic and morphological heterogeneity of commonly interrogated SWNT samples, and the fact that transient spectroscopic signals uniquely associated with the trion state have not been identified. Here length-sorted SWNTs and precisely controlled charge carrier-doping densities are used to determine trion dynamics using femtosecond pump-probe spectroscopy. Identification of the trion transient absorptive hallmark enables us to demonstrate that trions (i) derive from a precursor excitonic state, (ii) are produced via migration of excitons to stationary hole-polaron sites, and (iii) decay in a first-order manner. Importantly, under appropriate carrier-doping densities, exciton-to-trion conversion in SWNTs can approach 100% at ambient temperature. We further show that ultrafast pump-probe spectroscopy, coupled with these fundamental insights into trion formation and decay dynamics, enables a straightforward approach for quantitatively evaluating the extent of optically-driven free carrier generation (FCG) in SWNTs: this work provides fundamental new insights into how quantum yields for optically-driven FCG [Φ(Enn → h+ + e−)] in SWNTs may be modulated as functions of the optical excitation energy and medium dielectric strength. Collectively, these findings open up new possibilities for exploiting trions in SWNT optoelectronics, ranging from photovoltaics, photodetectors, to spintronics.
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    Halide perovskites: A new class of semiconductors with emergent properties

    Date:
    24
    Sunday
    February
    2019
    Lecture / Seminar
    Time: 15:00-16:00
    Location: Perlman Chemical Sciences Building
    Lecturer: Prof. Aditya Mohite
    Organizer: Department of Molecular Chemistry and Materials Science
    Abstract: Halide (hybrid) perovskites (HaP) have emerged as a new class of semiconductors ... Read more Halide (hybrid) perovskites (HaP) have emerged as a new class of semiconductors that truly encompass all the desired physical properties for building optoelectronic and quantum devices such as large tunable band-gaps, large absorption coefficients, long diffusion lengths, low effective mass, good mobility and long radiative lifetimes. In addition, HaPs are solution processed or low-temperature vapor grown semiconductors and are made from earth abundant materials thus making them technologically relevant in terms of cost/performance. As a result, proof-of-concept high efficiency optoelectronic devices such as photovoltaics and LEDs have been fabricated. In fact, photovoltaic efficiencies have sky rocketed to 23% merely in the past five years and are nearly on-par with mono-crystalline Si based solar cells. Such unprecedented progress has attracted tremendous interest among researchers to investigate the structure-function relationship and understand as to what makes Halide hybrid perovskites special? In my talk, I will attempt to answer some of the key questions and in doing so share the results from our work on HaPs over the past four years in understanding structure induced properties of HaPs. I will also highlight fundamental bottlenecks that exist going forward which present opportunities to create platforms to understand the interplay between light, fields and structure on the properties of perovskite-based materials.
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    Spotlight on Science

    Date:
    20
    Wednesday
    February
    2019
    Lecture / Seminar
    Time: 12:00
    Title: The 2018 Nobel Prize in Physics and how a simple trick changed optics forever
    Location: Arthur and Rochelle Belfer Building for Biomedical Research
    Lecturer: Dr. Barry Bruner

    Survival of the fittest, flattest, stabelest...

    Date:
    17
    Sunday
    February
    2019
    Lecture / Seminar
    Time: 13:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Yitzchak Pilpel, WIS
    Organizer: Department of Physics of Complex Systems
    Abstract: Evolution is “survival of the fittest”, but how is “fittest” defined? In ... Read more Evolution is “survival of the fittest”, but how is “fittest” defined? In simplest definitions, the fittest is the one who reproduces the fastest or with highest number of offspring. However, theories suggest that at certain situations others could be selected for. I will discuss two interesting cases. In communities that generate public goods, cooperators and defectors form more complicated evolutionary dynamics in which “fittest” depends on frequency of each strategy. Separately, the ability of evolution to select for the fastest reproducing variant is also balanced against the rate of mutations, and the quasi species theory predicts that at sufficiently high mutation rate the fastest might not necessarily be selected for. My lab employs synthetic DNA libraries and lab evolution to examine complex communities that reveal who really survives in evolution as a function of community structure and mutation rates. This very informal talk will present thoughts and challenges and preliminary results along these lines.
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    Symbolic dynamics for maps on surfaces

    Date:
    11
    Monday
    February
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Omri Sarig,
    Organizer: Department of Physics of Complex Systems
    Abstract: : I will review some of the ideas used by mathematicians to study the ergodic ... Read more : I will review some of the ideas used by mathematicians to study the ergodic theory of "chaotic" smooth invertible maps on surfaces. Symbolic dynamics allows to "change coordinates" and pass to a model similar to the configuration space of a 1D lattice gas model. Analogies to equilibrium statistical physics can then be employed to study the dynamic and stochastic properties of the system.
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    Chemical and Biological Physics Guest Seminar

    Date:
    10
    Sunday
    February
    2019
    Lecture / Seminar
    Time: 09:30
    Title: Computational Modeling of Large Biomolecular Systems: Methodology and a Case ‎Study of the Smartest Molecule (an NMDA Receptor in the Brain)
    Location: Perlman Chemical Sciences Building
    Lecturer: Dr. Anton V. Sinitskiy
    Organizer: Department of Chemical and Biological Physics
    Abstract: In this talk targeted at a wide audience of chemists, I will start with a story ... Read more In this talk targeted at a wide audience of chemists, I will start with a story about the ‘smartest’ molecule. Neuronal NMDA receptors, in my opinion, deserve this name, because they play the key role in the molecular mechanisms of learning, memory formation, and abstract reasoning. Also, malfunctioning NMDA receptors are involved in numerous neurological disorders, including schizophrenia, epilepsy, and Alzheimer’s disease. NMDA receptors are complicated and rich in behavior, and even the most up-to-date experimental methods yield only a fragmented picture of these biomolecules. How do their known structures relate to their biologically relevant functional states? Through what mechanisms do post-translational modifications (specifically, glycosylation) affect their physiological properties? Computational modeling offers unique insights into these questions, and I will outline my work in this field. Simulating NMDA receptors is a formidable task, though. In the second half of my talk, I will discuss how advances in methodology could facilitate studies of such large molecular and biomolecular systems. Specifically, I will focus on the concepts of coarse-graining, Markov state modeling, and mixed-resolution hybrid modeling, highlighting my work in this field [including ultra-coarse-grained modeling, and quantum mechanics / coarse-grained molecular mechanics (QM/CG-MM) approach]. Finally, I will briefly touch on the possible use of machine learning and deep learning networks in molecular modeling. In general, further advances in the theory and methodology of modeling will result in new opportunities for studying complex phenomena, such as learning and memory, with unprecedented resolution.
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    Towards a new understanding of disorder and dissipation in solids

    Date:
    04
    Monday
    February
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Alessio Zaccone
    Organizer: Department of Physics of Complex Systems
    Abstract: Solid-state theory has been formulated in the 20th century on the assumptions of ... Read more Solid-state theory has been formulated in the 20th century on the assumptions of regular crystalline lattices where linear dynamics holds at both classical and quantum levels, while dissipative effects are taken into account to perturbative order. While considerable success has been achieved in the further understanding of disorder effects on the electronic properties of solids, the same is not true for the thermal, vibrational and mechanical properties due to the difficulty of reformulating the whole body of lattice dynamics in a non-perturbative way for disordered systems. I will present a formulation of lattice dynamics extended (in a non-perturbative way) to disordered systems, called Nonaffine Lattice Dynamics (NALD), successfully tested on different systems [1-3]. I will then consider the effect of viscous dissipation on the lattice dynamics of crystalline solids and show how dissipation can lead, in perfectly ordered crystals, to effects very similar to disorder-induced effects in glasses. Theory can explain all these surprising effects in perfect crystals as a result of anharmonic damping inducing diffusive modes that compete with propagating modes [4], and also predicts similar effects resulting from low-lying soft optical phonons (experimentally confirmed). This framework may lead to a new quantitative connection between lattice/atomic parameters, electron-phonon coupling and the Tc of superconductors with the possibility, in future work, of rationalizing a variety of experimental data and to provide a more quantitative (less empirical) understanding of how Tc can be varied in conventional and perhaps also more exotic superconductors. [1] A. Zaccone and E. Scossa-Romano, Phys. Rev. B 83, 184205 (2011). [2] R. Milkus and A. Zaccone, Phys. Rev. B 93, 094204 (2016). [3] V.V. Palyulin, C. Ness, R. Milkus, R.M. Elder, T.W. Sirk, A. Zaccone, Soft Matter 14, 8475 (2018). [4] M. Baggioli and A. Zaccone, arXiv:1810.09516v1 [cond-mat.soft].
    Close abstract

    Towards a new understanding of disorder and dissipation in solids

    Date:
    04
    Monday
    February
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Alessio Zaccone
    Organizer: Department of Physics of Complex Systems
    Abstract: Solid-state theory has been formulated in the 20th century on the assumptions of ... Read more Solid-state theory has been formulated in the 20th century on the assumptions of regular crystalline lattices where linear dynamics holds at both classical and quantum levels, while dissipative effects are taken into account to perturbative order. While considerable success has been achieved in the further understanding of disorder effects on the electronic properties of solids, the same is not true for the thermal, vibrational and mechanical properties due to the difficulty of reformulating the whole body of lattice dynamics in a non-perturbative way for disordered systems. I will present a formulation of lattice dynamics extended (in a non-perturbative way) to disordered systems, called Nonaffine Lattice Dynamics (NALD), successfully tested on different systems [1-3]. I will then consider the effect of viscous dissipation on the lattice dynamics of crystalline solids and show how dissipation can lead, in perfectly ordered crystals, to effects very similar to disorder-induced effects in glasses. Theory can explain all these surprising effects in perfect crystals as a result of anharmonic damping inducing diffusive modes that compete with propagating modes [4], and also predicts similar effects resulting from low-lying soft optical phonons (experimentally confirmed). This framework may lead to a new quantitative connection between lattice/atomic parameters, electron-phonon coupling and the Tc of superconductors with the possibility, in future work, of rationalizing a variety of experimental data and to provide a more quantitative (less empirical) understanding of how Tc can be varied in conventional and perhaps also more exotic superconductors. [1] A. Zaccone and E. Scossa-Romano, Phys. Rev. B 83, 184205 (2011). [2] R. Milkus and A. Zaccone, Phys. Rev. B 93, 094204 (2016). [3] V.V. Palyulin, C. Ness, R. Milkus, R.M. Elder, T.W. Sirk, A. Zaccone, Soft Matter 14, 8475 (2018). [4] M. Baggioli and A. Zaccone, arXiv:1810.09516v1 [cond-mat.soft].
    Close abstract

    Semiconductor-Superconductor Hybrids, Qubits, and Topology

    Date:
    31
    Thursday
    January
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Charlie Markus
    Organizer: Faculty of Physics
    Details: 11:00 – coffee, tea, and more
    Abstract: A few years ago, the first signs of a new emergent particle — Majorana modes ... Read more A few years ago, the first signs of a new emergent particle — Majorana modes — were obtained. It was an exciting development because Majoranas are predicted to show nonabelian particle-exchange statistics, which would be a first for any physical system. As if that weren’t enough, another motivation to develop this experimental observation into a controlled electronic device is that the use of topology in such systems is expected to yield unrivalled coherence in topological qubits made from Majoranas. The experimental situation is that we aren’t there yet, not because of unforeseen problems — in fact, the foreseen problems are hard enough. This talk will address where things stand, how’s the qubit, what are the challenges, and what is the future of this unconventional approach to quantum information.
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    Stochastic pulse dynamics in a laser cavity

    Date:
    28
    Monday
    January
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Omri Gat
    Organizer: Department of Physics of Complex Systems
    Abstract: The interplay of nonlinear absorption and noise in mode locked lasers turns the ... Read more The interplay of nonlinear absorption and noise in mode locked lasers turns the process of pulse formation into a non-equilibrium phase transition. The pulses can be regarded as liquid drops immersed in vapor of low intensity quasi-continuum light. The pulses have well-defined shape and amplitude, and diffuse by interaction with the noisy continuum. Subtle effects of gain dynamics bias the diffusion, inducing a long-range noise-mediated interaction that is reminiscent of the Casimir effect in quantum electrodynamics. The noise-mediated interaction are shown to underpin the spectacular complex pulse motion in the ‘soliton rain’ laser operating regime.
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    Time and fundamentals of quantum mechanics

    Date:
    27
    Sunday
    January
    2019
    -
    01
    Friday
    February
    2019
    Conference
    Time: 08:00
    Location: David Lopatie Conference Centre

    Playing with a quantum toy: Exploring thermalization near integrability with a magnetic quantum Newton's cradle

    Date:
    24
    Thursday
    January
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Benjamin Lev
    Organizer: Faculty of Physics
    Details: 11:00 coffee tea and more
    Abstract: Thermalization of near-integrable quantum systems is an unresolved question. We ... Read more Thermalization of near-integrable quantum systems is an unresolved question. We will present a new experiment that explores the emergence of thermalization in a quantum system by studying the dynamics of the momentum in a dipolar quantum Newton's cradle consisting of highly magnetic dysprosium atoms. This system constitutes the first dipolar strongly interacting 1D Bose gas. These interactions provide tunability of both the strength of the integrability-breaking perturbation and the nature of the near-integrable dynamics. The work sheds light on the mechanisms by which isolated quantum many-body systems thermalize and on the temporal structure of the onset of thermalization. We anticipate our novel 1D dipolar gas will yield insights into quantum thermalization and strongly interacting quantum gases with long-range interactions.
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    On the mechanics of leaves, flowers, and sea-slugs

    Date:
    20
    Sunday
    January
    2019
    Lecture / Seminar
    Time: 13:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Shankar Venkataramani
    Organizer: Department of Physics of Complex Systems
    Abstract: I will discuss some connections between the geometry and the mechanics of thin e ... Read more I will discuss some connections between the geometry and the mechanics of thin elastic objects with negative curvature. I will motivate the need for new "geometric" methods for discretizing the relevant equations, and present some of our preliminary work in this direction. This is joint work with Toby Shearman and Ken Yamamoto.
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    Imaging Topological Materials

    Date:
    17
    Thursday
    January
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Prof. Jenny Hoffman
    Organizer: Faculty of Physics
    Details: 11:00 – coffee, tea, and more
    Abstract: Today’s electronic technology – the pixels on the screen and the process to ... Read more Today’s electronic technology – the pixels on the screen and the process to print the words on the page – are all made possible by the controlled motion of an electron’s charge. In the last decade, the discovery of topological band insulators with robust spin-polarized surface states has launched a new subfield of physics promising a new paradigm in computing. When topology is combined with strong electron correlations, even more interesting states of matter can arise, suggesting additional applications in quantum computing. Here we present the first direct proof of a strongly correlated topological insulator. Using scanning tunneling microscopy to probe the real and momentum space structure of SmB6, we quantify the opening of a Kondo insulating gap. Within that gap, we discover linearly dispersing surface states with the heaviest observed Dirac states in any material – hundreds of times the mass of a free electron. We show how single atom defects can scatter these surface states, which paves the way towards manipulating single atoms and thus controlling surface states and their excitations at the nanoscale.
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    Prof. Roee Ozeri - Quantum computers: taming Schrodinger's cat

    Date:
    15
    Tuesday
    January
    2019
    Lecture / Seminar
    Time: 12:00
    Title: Quantum computers: taming Schrodinger's cat
    Location: Dolfi and Lola Ebner Auditorium
    Lecturer: Prof. Roee Ozeri
    Organizer: Communications and Spokesperson Department
    Details: The lecture is in Hebrew

    Transport and condensation in the quantum-classical limit of open quantum systems

    Date:
    14
    Monday
    January
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Ohad Shpilberg
    Organizer: Department of Physics of Complex Systems
    Abstract: The Lindblad equation allows to explore general properties of open quantum syste ... Read more The Lindblad equation allows to explore general properties of open quantum systems. Whenever strong decoherence processes are present, one expects the system to become classical. Namely, the evolution of the surviving diagonal terms of the density matrix is Markovian. Surprisingly enough, many interesting aspects of the quantum system can be inferred from the classical limit. Among which we will explore some transport properties as well as a condensation transition for interacting quantum particles. Moreover, we will be interested in the quantum corrections to Fick’s law in diffusive systems
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    New Insight into Cosmology and the Galaxy-Halo Connection from Non-Linear Scales

    Date:
    10
    Thursday
    January
    2019
    Colloquium
    Time: 11:15-12:30
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Frank C. van den Bosch
    Organizer: Faculty of Physics
    Details: 11:00 – coffee, tea, and more
    Abstract: In our LCDM paradigm, galaxies form and reside in dark matter halos. Establishin ... Read more In our LCDM paradigm, galaxies form and reside in dark matter halos. Establishing the (statistical) relation between galaxies and dark matter halos, the `Galaxy-Halo connection', therefore gives important insight into galaxy formation, and also is a gateway to using the distribution of galaxies to constrain cosmological parameters. After a brief introduction to how clustering and gravitational lensing can be used to constrain the galaxy-halo connection, I show that several independent analyses all point towards a significant tension in cosmological parameters compared to the recent CMB results from the Planck satellite. I discuss the potential impact of assembly bias, and present satellite kinematics as a complementary and competitive method to constrain the galaxy-halo connection. After a brief historical overview of the use of satellite kinematics, I present two new analyses, and show how they can be used to improve our knowledge of the galaxy-halo connection.
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    Universal features in disordered solids: Implications for directed aging and the creation of non-linear metamaterials

    Date:
    07
    Monday
    January
    2019
    Lecture / Seminar
    Time: 14:15
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Daniel Hexner
    Organizer: Department of Physics of Complex Systems
    Abstract: The most obvious and distinctive feature of an amorphous solid is its heterogene ... Read more The most obvious and distinctive feature of an amorphous solid is its heterogeneous microscopic structure. A central issue is how such disorder governs the elastic properties of an amorphous solid so that it has different behavior from its crystalline counterpart. I will show how such disorder on the microscale determines the elastic properties on long length scales. This theoretical approach ultimately allows us to control a material’s elastic properties and to understand how a material ages and stores memories. I start by studying the change in an amorphous solid’s elastic properties upon the removal of a single bond. I show that the change in moduli, which has a broad and universal shape, is uncorrelated for different imposed strains. Thus, by selectively removing a small number of bonds, the precise global and local elastic behavior of the solid can be controlled. This in turn suggests that small changes in bond properties, which occur naturally as a solid ages, can dramatically alter the solid’s elastic response; the history of imposed strains is encoded in the non-linear response and the aging process, usually considered to be detrimental, can be harnessed to design materials with novel desired properties.
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    Non-linear dynamics of beating cardiac cells

    Date:
    06
    Sunday
    January
    2019
    Lecture / Seminar
    Time: 13:00
    Location: Edna and K.B. Weissman Building of Physical Sciences
    Lecturer: Sam Safran
    Organizer: Department of Physics of Complex Systems
    Abstract: The observation of spontaneous calcium oscillations of ~ 1Hz in beating cardia ... Read more The observation of spontaneous calcium oscillations of ~ 1Hz in beating cardiac cells is typically explained by many coupled chemical reactions and parameters. We show that the separation of time scales of fast processes with slower calcium diffusion in the cell results in a single, non-linear dynamical equation that characterizes these oscillations with only a few physically relevant parameters. Motivated by recent experiments, we predict how the beating can be entrained to an external, oscillatory electric or mechanical strain field and compare our predictions for the onset of entrainment to measurements. We further demonstrate, both experimentally and theoretically, that a much slower time scale (minutes to hours) can be extracted from analysis of the noisy dynamics of beating.
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    Example 1 for internal event node

    Date:
    08
    Monday
    May
    2017
    -
    10
    Wednesday
    May
    2017
    Retreat
    Time: 10:00 - 12:30
    Location: David Lopatie Conference Centre ...
    Organizer: Department of ...

    Example 2 for internal event node

    Date:
    08
    Monday
    May
    2017
    -
    10
    Wednesday
    May
    2017
    Retreat
    Time: 10:00 - 12:30
    Location: David Lopatie Conference Centre ...
    Organizer: Department of ...