Events
Particles and Fields Seminar
Universality driven analytic structure of QCD crossover
Vladimir Skokov
North Carolina State University
Mon, 19 Apr 2021, 14:00
Zoom
Abstract: As a system is tuned away from a second-order phase transition into the crossover region, the critical point splits into a pair of complex conjugate singularities lying at complex values of the system parameters - the Yang-Lee edge (YLE) singularities. These singularities can be treated as ordinary critical points belonging to a specific universal class. For Quantum ChromoDynamics in the O(4) crossover regime, this translates into a critical point at complex values of the baryon chemical potential. In this seminar, I will tell you about the first study of these universal locations for the 3d O(N) universality classes using the functional renormalization group. I will discuss the relevance of the YLE for QCD and the search for the QCD critical point.
Zoom link will be sent separately.
Physics Colloquium
Visualizing the Quantum Phases of Magic Angle Graphene
Shahal Ilani
Weizmann Institute
Mon, 19 Apr 2021, 16:10
Zoom
Abstract: Twisted bilayer graphene near the magic angle exhibits a remarkable array of quantum phases, whose nature and origin are still poorly understood. In this talk I will describe our nanotube-based scanning single-electron-transistor (SET) experiments that explore and visualize some of these phases. Nanotube SET is an extremely sensitive electrometer, capable of probing a variety of thermodynamic properties of electrons on the nanoscale. By measuring the electronic compressibility [1], we reveal a cascade of spin/valley symmetry-breaking phase transitions. This cascade appears at temperatures well above the onset of the superconducting and correlated insulating phases, demonstrating that it forms the parent state out of which these phases emerge. Measurements of the electronic entropy [2] reveal that magic angle graphene exhibits a curious analog of the Pomeranchuk effect in 3He. In 3He, counterintuitively, the liquid can solidify upon heating, owing to a large spin entropy of the solid. Here we measure a similar giant magnetic entropy (~1kB per moiré site) near a filling of one electron per moiré site. This entropy drives a Pomeranchuk-like transition from a rather conventional metal to a correlated state with nearly-free magnetic moments. However, while in 3He it is easy to understand why the spins of localized atoms in the solid are practically free, it is very surprising to observe nearly-free moments in a metallic, compressible state, making the nature of this newly observed correlated state highly puzzling.
[1] Zondiner, U. et al., Nature 582, 203–208 (2020).
[2] Rozen, A. et al., Nature 592, 214-219 (2021).
*** The Zoom link will be sent to all the department members on the day of the event. ***
Condensed Matter Seminar
Floquet-engineered topological phases and probes of quantum matter
Prof. Babak Seradjeh
Indiana University
Tue, 20 Apr 2021, 18:00
Zoom *** Note the date/time change ***
Abstract: I will present our recent and ongoing work on proposed realizations, detection, and applications of non-equilibrium topological phases of matter engineered and stabilized by external periodic drives. These include Floquet topological insulators and superconducting phases that can support multiple topological bound states, various phases of irradiated graphene under circularly polarized lasers, and higher-order topological phases that support corner and bulk bound states. I will also discuss novel dynamical responses of driven systems and Floquet gauge pumps as probes of protected many-body degeneracies. A central theme of this work is the exquisite in-situ control offered by Floquet engineering allowing the realization and study of novel quantum phases of matter.
Join Zoom Meeting
https://us02web.zoom.us/j/89262629053?pwd=QWFaaTF5RUJUb0ROQzhiYklieE1qZz09
Astrophysics and Cosmology Seminar
Mind the gap: What can we learn about stellar astrophysics from gravitational wave detections of binary black holes?
Dr. Rob Farmer
University Of Amsterdam
Wed, 21 Apr 2021, 11:10
Sacta-Rashi Building for Physics (54), room 207
Abstract: With the detection of binary black hole (BH) mergers from LIGO/Virgo we have opened up the field of gravitational wave astronomy and created a new window into the Universe. These discoveries bring new and independent information about how very massive stars end their life, and the final remnants they leave behind. In this talk I will discuss the stellar physics that goes into the formation of the most massive stellar mass black holes and how the detection of most massive merging pair of black holes to date, GW190521, with both BHs being in the “PISN mass gap” challenges this picture. I will show what physics goes into the location of this mass gap, and how robust we believe the estimate of the location of the mass gap is. I will then discuss what GW190521 informs us about the location of the mass gap, and the implications for finding both black holes in the mass gap. Finally, I will also discuss how measuring the location of the mass gap allows us to place constraints on uncertain stellar physics, namely the C12(alpha,gamma)O16 nuclear reaction rate and what GW190521 can tell us about this nuclear reaction rate.
Quantum optics seminar
Dressed potentials with coherence control for trapped atom interferometry
Prof. Thomas Fernholz
University Of Nottingham
Wed, 21 Apr 2021, 15:00
ZOOM
Abstract: ZOOM link: https://us02web.zoom.us/j/88535113048
ABSTRACT: On the quest to building a fully trapped atom interferometer, we investigate state-dependent trapping of ultra-cold rubidium atoms in radio-frequency dressed potentials. In this talk I will discuss trapping topologies for the implementation of a Sagnac interferometer that is sensitive to rotation. As the interferometer sequence is akin to the operation of an atomic clock, I will present our analysis of the radio-frequency dressed hyperfine spectrum. We identified suitable transition frequencies, clarified the compatibility of the required microwave polarisation with an atomchip trap, and experimentally investigated additional microwave dressing to reduce incoherent broadening in trapped thermal ensembles. I will also report on the current status of the atomchip-based interferometer setup.
Biological and soft-matter physics
Mathematical essence of aging
Prof. Uri Alon
Dept. Of Molecular Cell Biology, Weizmann Institute Of Science
Thu, 22 Apr 2021, 12:10
ZOOM only - Meeting ID: 874 2021 0979
Abstract: Aging of humans and other organisms shares nearly-universal features, hinting at understandability. With age, the risk of death and of many diseases rises exponentially, health differences between individuals widen, and timescales for recovery grow longer. Aging, at least in mice, seems reversible to a certain extent, as evidenced by experiments which remove damaged cells or enhance repair. These features lead to a theory of the core processes of aging using a stochastic equation for damage accumulation. In this equation, mutated stem cells give rise to damaged cells which inhibit their own removal by the immune system. We back this up with experiments on a key type of damaged cells, called senescent cells, whose removal has been shown to rejuvenate mice. The mathematical approach explains the incidence curves of age-related diseases in humans, and the scaling and dynamics of survival curves under life-span-extending interventions in model organisms. It provides mechanisms for several diseases of unknown origin. We will discuss how this approach might guide future optimal treatment for aging.
Join Zoom Meeting
https://us02web.zoom.us/j/87420210979
Meeting ID: 874 2021 0979
Condensed Matter Seminar
A minimal model for many body localization transitions
Prof. Alex Altland
University Of Cologne
Mon, 26 Apr 2021, 11:10
Zoom only
Abstract: The Sachdev-Ye-Kitaev (SYK) model is a system of a large number of randomly interacting Majorana fermions. A unique feature of the model is that it displays the full complexity of many body chaos and strong correlations, and at the same time is simple enough to be amenable to analytic solution schemes. In this talk we will discuss the physics of the SYK model perturbed by a one-body Hamiltonian inducing an ergodic to Fock space many body localization (MBL) transition at a critical coupling strength. We discuss the qualitative physics of the transition, its quantitative description, and where it differs from the MBL transition in spatially extended geometries. In the final part of the talk we discuss how the lessons learned from this ’null-model’ of MBL may be relevant to the operability of current date quantum computing architectures building on the transmon qubit platform.
Biological and soft-matter physics
TBA
Prof. Haim Diamant
School Of Chemistry, Tel-Aviv University
Thu, 29 Apr 2021, 12:10
subject to changes: Sacta-Rashi Building for Physics (54), room 207
Abstract:
All events
Google calendar
