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Events on Thursday, January 18th, 2024

Graduate Program Event
Qualifying Exam - Classical Mechanics
Time: 9:00 am - 10:30 am
Place: 2241 Chamberlin
Host: Sharon Kahn
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R. G. Herb Condensed Matter Seminar
Inelastic decay from integrability
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Amir Burshtein, Tel Aviv U
Abstract: Recent experiments in circuit QED setups have demonstrated the high probability splitting of single-photons, a phenomenon rarely observed in nature. This exotic effect is enabled by a high-impedance Josephson transmission line which increases the effective coupling of the microwave photons to an artificial atom, and provides a useful tool to probe fundamental phenomena in many-body systems.
I will discuss a collaboration with the Kuzmin group, in which we utilized single-photon splitting to observe the Schmid-Bulgadaev quantum phase transition, whose lack of clear evidence has sparked a recent debate. The experimental system realizes the boundary sine-Gordon model, which is known to be integrable and is characterized by purely elastic scattering of elementary excitations, that seems at odds with photon splitting. I will show that a nonlinear relation between these excitations and the photons not only allows for inelastic decay of the latter, but also that integrability provides powerful analytical tools yielding exact results for the total inelastic decay rate and the spectrum of the resulting photons. Our results shed light on the Schmid-Bulgadaev transition, and compare nicely with experimental measurements.

Host: Roman Kuzmin
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NPAC (Nuclear/Particle/Astro/Cosmo) Forum
Probing Cosmic Ray Physics at TeV-PeV Energies with GRAPES-3 Experiment
Time: 10:30 am - 11:30 am
Speaker: Pravata Kumar Mohanty, Tata Institute of Fundamental Research, Mumbai
Abstract: The GRAPES-3 experiment located in Ooty, India employs a dense array of plastic scintillator detectors and a large area muon detector to measure all charged particles and muonic components in cosmic ray showers, respectively. Recently, we reported the measurement of the proton spectrum of cosmic rays from 50 TeV 1.3 PeV, with a significant hardening observed at around 166 TeV. The new feature contradicts the long-held belief that the cosmic ray spectrum follows a single power-law up to the knee energy and may require more complex models such as those where classes of sources with different cutoffs contribute to the flux. Additionally, we have reported the observation of two significant small-scale anisotropic structures in the cosmic ray arrival distribution, consistent with the observations of HAWC and ARGO-YBJ experiment. In this talk, I will provide an overview of the GRAPES-3 experimental setup, discuss the above mentioned results, and tell about the ongoing upgrade activities and future plans.
Host: Sanjib Kumar Agarwalla
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Graduate Program Event
Qualifying Exam - Statistical Mechanics
Time: 11:30 am - 1:00 pm
Place: 2241 Chamberlin
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