People by Discipline

Name	Discipline	Category	Phone	Office
Teboul Odelia	Astrophysics and Relativity	Graduate Students
Thaler Irina	Astrophysics and Relativity	Post-Docs
Ziskin Shlomi	Astrophysics and Relativity	Post-Docs
Rom Barak	Astrophysics and Relativity	Graduate Students	02 6585 529	Kaplun Bldg.
Sari Reem	Astrophysics and Relativity	Faculty	02 6585 806	Kaplun 111
Freundlich Jonathan	Astrophysics and Relativity	Post-Docs	02 6584 675	Kaplun 201
Horesh Assaf	Astrophysics and Relativity	Faculty	02 6584 928	Kaplun Bldg. 110
Benyamin David	Astrophysics and Relativity	Post-Docs		Kaplun 100
Chan Chi Ho (Edwin)	Astrophysics and Relativity	Post-Docs	02 6584 997	Kaplun 101
Piran Tsvi	Astrophysics and Relativity	Faculty	02 6584 233	Kaplun 108

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Upcoming Events

Yesterday

Condensed-Matter Seminar: "Mott Materials, Correlation Strength, Surfaces and Device Dreams"
- Start time: 12:00pm
- End date: Thursday, April 3rd
- End time: 01:30pm
- Lecturer: Lior Kornblum, Andrew & Erna Viterbi Dept. of Electrical & Computer Engineering, Technion, HaifaAbstract:Electron correlation is responsible for countless interesting condensed matter phenomena.Oxides with electron correlation provide an attractive testbed for many of those, wherecoupling between the spin, charge and lattice degrees of freedom can be tweaked andexplored. Our work started with strontium vanadate (SrVO 3 ) as a simple test case of theMott-Hubbard type of correlated electronic structure. We harness advanced thin filmsynthesis techniques to control the correlation strength by tuning the degree of orbitaloverlap using picometer-scale lattice engineering. We illustrate how bandwidth control andconcurrent symmetry breaking can govern the electronic structure of this SrVO 3 modelsystem. This shows how tensile and compressive biaxial strain oppositely affect the SrVO 3 in-plane and out-of-plane orbital occupancy, resulting in the partial alleviation of the orbitaldegeneracy. The spectral weight redistribution under strain is derived and explained,illustrating how tensile strain drives the system toward a Mott insulating state. The criticalrole of the surface chemistry in this picture will be addressed. This picture, derived from asimple and clean system, can shed light on other more complex examples.Pivoting from the simple SrVO 3 system, we studied films of La 1-x Sr x VO 3 , a filling-controlledMott system where the number of free electrons and the electronic phase can bemanipulated by the composition. From this system, we crafted a back-gated (solid state)field-effect device with a correlated, Mott channel. With this rudimentary device, wedemonstrate that with increasing the electron density in the electron channel, the resistanceactually increases. This behavior is explained by an increase in the correlation strength dueto the increase in electron-electron interaction. The effect on resistivity is ×10 larger thanthe change in the electron density, and we show that it is actually as much as ×100 due toscreening of the field. We will discuss our vision for crafting this limited demonstrator into adevice that might be practical one day.
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Special Astrolunch: Ore Gottlieb
- Start time: 12:30pm
- End date: Thursday, April 3rd
- End time: 01:30pm
- Speaker: Dr. Ore Gottlieb (Center for Computational Astrophysics, Flatiron Institute, New York, USA)Title: Using Multi-scale Simulations to Probe the Physics of Multi-messenger TransientsAbstract:With the advent of next-generation multi-messenger observatories (e.g., LIGO O4-O5 and Rubin), multi-messenger events will offer unprecedented opportunities to address profound questions in black hole physics, heavy element nucleosynthesis, jet dynamics, cosmic expansion, and the origin of high-energy particles. Yet, the enormous dynamical range separating the black hole from the emission region has posed significant challenges for theoretical models seeking to connect observations with underlying physics. I will present the first 3D neutrino-general relativistic magnetohydrodynamic simulations that bridge this gap. I will demonstrate how combining these large-scale simulations with analytic modeling and observational data marks a first step toward transforming time-domain astronomy by:1. Interpreting observations from first principles - for example, resolving long-standing mysteries in gamma-ray burst observations;2. Utilizing observational data to probe extreme physics, such as the natal properties of black holes and the engines powering the universe’s most luminous explosions; and3. Predicting new, detectable multi-messenger sources, including kilonovae and gravitational waves from accretion disks in collapsing stars.This integrated approach sheds new light on transient observations and sets the stage for transformative discoveries in multi-messenger astrophysics.Zoom link:https://huji.zoom.us/j/85193525500?pwd=fxw6VUlnT6vzHmXubvatDBrGaDh68w.1Meeting ID: 851 9352 5500Passcode: 736788 Contact: Sivan Ginzburg
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Sunday, April 6th

Special Astrolunch: Mor Rozner
- Start time: 02:00pm
- End date: Sunday, April 6th
- End time: 03:00pm
- Speaker: Dr. Mor Rozner (Gonville & Caius College, Cambridge, UK; Institute for Advanced Study, Princeton, NJ, USA)Title: From Few-Body to Stellar Clusters: How Gas Reshapes Dynamical Evolution Abstract:Gas-rich environments are ubiquitous in various scales, from protoplanetary disks to star clusters and galaxies. Dynamics in gas-rich environments are substantially different and give rise to unique astrophysical phenomena, along with enhancing the rates of well-studied phenomena. In this talk, I will outline some of my work on dynamics in gas-rich environments. Nuclear star clusters (NSCs) are dense star clusters that reside at the centers of many galaxies. Due to their high densities, they serve as fertile grounds for various processes that are otherwise rare in less dense environments. The stellar distribution within NSCs is an important parameter in determining the rates of these events. NSCs can contain substantial amounts of gas, which reshape their stellar distributions and lead to steeper stellar cusps. I will re-derive and generalize the Bahcall-Wolf distribution to account for the effects of the added gas and discuss its implications for the rates of tidal disruption events (TDEs) and other transients in galactic nuclei.Binaries in dense environments are traditionally classified as soft or hard based on their binding energy relative to the kinetic energy of surrounding stars. Heggie’s law suggests that stellar encounters tend to soften soft binaries and harden hard binaries, altering their separations. However, interactions with gas in such environments can significantly modify this behavior. I will discuss the impact of gas on binary softening and its consequences. I will show that gas interactions can actually harden binaries, extending the soft–hard boundary to larger separations. This introduces a “shielding radius” within which binaries are likely to harden due to gas interactions, surpassing the traditional soft–hard limit. Consequently, a notable portion of binaries initially classified as “soft” may become “hard” when both gas and stars are considered. While the exact criteria for common envelope (CE) formation are still uncertain, it is generally suggested that the binary pericenter should be small to initiate an unstable mass transfer. Hence, CE formation is expected to be more prevalent in gas-rich environments, including clusters hosting multiple populations, which are expected to be the majority of globular clusters. In these clusters, the existence of a second (or further) population of stars suggests a significant secondary epoch of gas, to support the formation of the second population of stars.If time allows, I will discuss the von-Zeipel Lidov Kozai mechanism in gas-rich environments. All the binaries in active galactic nuclei (AGNs) are essentially triples with the central black hole as a third perturber. Also here, the interaction with gas could modify significantly the evolution and introduce new regimes of dynamical behavior. Zoom link:https://huji.zoom.us/j/83997062083?pwd=db4qOST79w7aQcYfrCUzRVr2toZjgy.1Meeting ID: 839 9706 2083Passcode: 231948 Contact: Sivan Ginzburg
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Monday, April 7th

Physics Colloquium : "Detection of Entanglement by Stimulated Disentanglement"
- Start time: 12:00pm
- End date: Monday, April 7th
- End time: 01:30pm
- Lecturer: Avi Pe'er, Bar IlanAbstract:Standard detection of entanglement relies on local measurements of the individual particles, evaluating their correlations in post-processing. For time-energy entangled photons, either times (t1,t2) or energies (E1,E2) are measured, but not both due to the mutual quantum uncertainty, providing only partial information of the entanglement. In principle, a global detector could recover the complete information of entanglement in a single shot if it could measure the combined correlated variables (t1-t2) and (E1+E2) without measuring the individual energies or times. Such a global measurement is possible using the reverse disentangling interaction, like sum-frequency generation (SFG), but nonlinear interactions at the single-photon level are exceedingly inefficient. We overcome this barrier by stimulating the nonlinear SFG interaction with a strong pump, thereby measuring both the energy-sum (SFG spectrum) and the time-difference (response to group delay/dispersion) simultaneously and efficiently. We generate biphotons with extreme time-energy entanglement (octave-spanning spectrum of 113THz) and measure a relative uncertainty between time-difference and energy-sum of D(t1-t2)D(E1+E2)=2X10-13h, violating the classical bound by more than 12 orders of magnitude. The presented coherent SFG dramatically enhances the detection SNR compared to standard methods since it ideally rejects erroneous coincidences in both time and energy, paving the way for sensing applications, such as quantum illumination (radar) and more.
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Tuesday, April 8th

Astrolunch: Tal Wasserman
- Start time: 12:30pm
- End date: Tuesday, April 8th
- End time: 01:30pm
- Speaker: Tal Wasserman (Weizmann Institute of Science) Title: The Optical to X-ray Luminosity and Spectrum of Supernova Wind Breakouts I will discuss our recent work on the breakout of SN shock waves through extended dense circum-stellar media (CSM) that observations indicate are common at radii of 10^14 – 10^15 cm around core-collapse SN progenitors. The breakout of the radiation-mediated shock (RMS) through such CSM leads to the formation of a collisionless shock (CLS). We analyze the evolution of the shock structure and associated radiation field during and after the RMS-CLS transition for non-relativistic breakouts. We provide an analytic description of the key properties of the emitted optical to X-ray radiation, supported by numeric radiation-hydrodynamics calculations. We show that the characteristic photon energy shifts from the UV to X-rays as the shock moves to a few breakout radii on a few breakout timescales (days), and that the X-ray signal is not suppressed by propagation through the upstream wind. Upcoming surveys that will systematically detect large numbers of young SNe will enable the use of these results to infer the pre-explosion mass loss history of the SN progenitor population.Zoom link:https://huji.zoom.us/j/82440715494?pwd=aaeSQpFMyrnuJKrbW8uZjUNx60Rm92.1Meeting ID: 824 4071 5494Passcode: 740718Contact: Dima Ofengeim
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Wednesday, April 9th

Nonlinear Physics seminar: "Emergent Disorder and Mechanical Memory in Periodic Metamaterials"
- Start time: 12:00pm
- End date: Wednesday, April 9th
- End time: 01:30pm
- Lecturer: Prof. Yair Shokef, Tel-Aviv University
  
  Abstract:
  Ordered mechanical systems typically have one or only a few stable rest configurations, and hence are not considered useful for encoding memory. Multistable and history-dependent responses usually emerge from quenched disorder, for example in amorphous solids or crumpled sheets. Inspired by the topological structure of frustrated artificial spin ices, we introduce an approach to design ordered, periodic mechanical metamaterials that exhibit an extensive set of spatially disordered states. We show how such systems exhibit non-Abelian and history-dependent responses, as their state can depend on the order in which external manipulations were applied. We demonstrate how this richness of the dynamics enables to recognize, from a static measurement of the final state, the sequence of operations that an extended system underwent. Thus, multistability and potential to perform computation emerge from geometric frustration in ordered mechanical lattices that create their own disorder.
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Thursday, April 10th

Condensed-Matter Seminar
- Start time: 12:00pm
- End date: Thursday, April 10th
- End time: 01:30pm
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