Yacoby Yizhak

Job/Title:

Joseph and Sadie Danciger Chair of Physics

Primary Category:

Emeriti

Discipline:

Condensed Matter Physics

Office:

Danciger B 119

Phone:

02 6585 849

Fax:

02 6586 168

E-Mail:

Home Page:

http://www.phys.huji.ac.il/~yizhak/

Upcoming Events

Yesterday

ZOHAR RINGEL
- Start time: 10:30am
- End date: Tuesday, December 10th
- End time: 12:00pm
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Quantum Physics Seminar: ""
- Start time: 12:00pm
- End date: Tuesday, December 10th
- End time: 01:30pm
- Lecturer: Hagai Diamandi (Applicant) Abstract:
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astrolunch: Fabio Pacucci
- Start time: 05:00pm
- End date: Tuesday, December 10th
- End time: 06:00pm
- Title: JWST's Little Red Dots: Masters of Disguise in the High-Redshift Universe This talk will explore the exciting journey to probe several populations of black holes, spanning from the distant to the local Universe. I will focus primarily on the "little red dots" (LRDs), a newly discovered and puzzling population of compact red sources at redshift z > 4, identified by JWST. These objects challenge our current astrophysical models in several ways. First, I will discuss the detection of overmassive black holes relative to the stellar mass of their host galaxies. Second, I will address the X-ray weakness problem, where these sources remain undetected in deep X-ray surveys. I will use advanced GRRMHD simulations to show how mildly super-Eddington accretion onto slowly spinning black holes can resolve this issue. Third, I will explore the extremely high stellar densities at the cores of these objects and their potential for triggering runaway stellar collisions. Throughout the talk, I will also discuss how the LRDs represent a perfect bridge to study other populations of black holes, with a focus on the role of future observatories such as HWO and AXIS. These include the search for black hole seeds at redshifts z = 20-30 and the detection of quiescent black holes in the local Universe.Bio: Fabio Pacucci is a Clay and BHI Fellow at the Center for Astrophysics. He obtained his PhD in Physics from the Scuola Normale Superiore in Pisa, Italy.He is an expert in the theory and observations of high-z black holes and is part of several large JWST programs.He is also involved in planning next-generation observatories, such as NASA's AXIS in the X-ray, which was just selected for Phase A, and HWO in the UV, optical, and infrared, which will be NASA's next flagship mission.contact: Zhaozhou
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Monday, December 16th

Physics Colloquium : "IS EARTH EXCEPTIONAL?"
- Start time: 12:00pm
- End date: Monday, December 16th
- End time: 01:30pm
- Lecturer: Mario Livio ( Rosenblum Prize )Abstract:The questions “How did life on Earth begin?” and “Are we alone in the universe?” are arguably two of the most intriguing in science. While until recently these questions tended to be relegated to the “too difficult” box, the attempts to answer them have now become extraordinarily vibrant and dynamic frontiers of science.I will describe how the quest for cosmic life follows two parallel, independent lines of research: cutting-edge laboratory studies aimed at determining whether life can emerge from pure chemistry, and advanced astronomical observations searching for signs of life on other planets and moons in the solar system and around stars other than the Sun. I will examine how using knowledge acquired through ingenious chemical experimentation, geological studies, advanced astronomical observations, and imaginative theorizing researchers have managed to delineate a plausible pathway leading from the formation of the Earth to the appearance of the early biological cells.
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Tuesday, December 17th

Astrolunch: David Chay Benisty
- Start time: 12:30pm
- End date: Tuesday, December 17th
- End time: 01:30pm
- Multiscale Constraints on Dark Energy: From Pulsars and the Local Group to CosmologyIn this talk, I will explore constraints on dark energy beyond the standard cosmological frameworks, incorporating insights from binary motion and galactic dynamics. I will present a method to constrain the cosmological constant, Λ, using binary galaxy systems. The ratio between the Keplerian orbital period and TΛ≈35 Gyr determines the significance of cosmological constant effects on binary motion. For systems with periods approaching this timescale, the influence of Λ becomes significant. The Milky Way–Andromeda (M31) system, with an orbital period of ∼17 Gyr, requires the inclusion of dark energy effects. Utilizing the latest mass estimates for the Milky Way and M31, combined with proper motion data from HST and Gaia, I will demonstrate that the value of Λ inferred from Local Group dynamics is less than 5.44 times the Planck value. Furthermore, I will discuss a general framework for applying constraints to galaxy groups and clusters in the local universe.Contact: Zhaozhou Li
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Yacoby Yizhak