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Events on Wednesday, February 8th, 2023

Preliminary Exam
Searches for transient astrophysical neutrino sources with IceCube
Time: 10:00 am
Place: 4274 Chamberlin
Speaker: Jessie Thwaites, Physics Graduate Student
Abstract: Multi-messenger astrophysics is a powerful tool for understanding the most energetic sources in the universe. Although IceCube has discovered a flux of extragalactic neutrinos, the sources of the vast majority of those neutrinos remain a mystery. We describe searches for neutrino emission from transient astrophysical source classes, both in archival searches and real-time analyses. In archival data, we use IceCube-DeepCore to search for GeV neutrinos from novae, and set the first upper limits on neutrinos from novae. We describe a planned search for neutrinos from fast radio bursts (FRBs) using the first catalog published by the CHIME/FRB Collaboration, which provides more than an order of magnitude more sources than previous IceCube FRB searches. We also describe real-time follow-up searches for neutrinos from astrophysical transients, including for the brightest gamma-ray burst ever recorded, GRB 221009A, for which we report a non-detection and set strong constraints on neutrino emission. We also describe planned follow-ups of gravitational wave events during LIGO-Virgo-KAGRA operating run 4, which is anticipated to start providing alerts as early as mid-February 2023.
Host: Justin Vandenbroucke
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Physics ∩ ML Seminar
Bayesian Renormalization: An explicit correspondence between statistical inference and exact renormalization
Time: 11:00 am
Place: Online Seminar: Please sign up for our mailing list at for zoom link
Speaker: Marc Klinger, University of Illinois Urbana-Champaign
Abstract: Renormalization is a ubiquitous tool in theoretical physics used to understand the role of scale in organizing natural phenomena. In this presentation we will report on a new information theoretic perspective for understanding the Exact Renormalization Group (ERG) through the intermediary of Bayesian Statistical Inference. This connection is facilitated by the Dynamical Bayesian Inference scheme, which encodes Bayesian inference in the form of a one parameter family of probability distributions solving an integro-differential equation derived from Bayes’ law. Utilizing the picture of an ERG flow as a functional diffusion process, we arrive at a dictionary outlining how renormalization can be understood as an inverse process relative to a Dynamical Bayesian inference scheme. A particularly salient feature of this correspondence is that it identifies the role of Fisher geometry in providing an emergent scale for “Bayesian Renormalization” that is related to the precision with which nearby points in model space can be differentiated. We comment on the usefulness of this identification in data science applications including possible implementations of “Bayesian Renormalization” as a tool for refining diffusion learning techniques.
Host: Gary Shiu
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Atomic Physics Seminar
Quantum many-body physics with ultracold molecules
Time: 11:00 am
Place: 5310 Chamberlin Hall
Speaker: Zoe Yan , Princeton University
Abstract: A central challenge of modern physics is understanding the behavior of strongly correlated matter. Current knowledge of such systems is limited on multiple fronts: experimentally, these materials are often difficult to fabricate in laboratory settings, and numerical simulations become intractable as the number of particles approaches meaningful values. In the spirit of Feynman, physicists can model diverse phenomena, from high-temperature superconductivity to quantum spin liquids, using analog quantum simulation. My research explores emergent quantum phenomena in pristine systems made of atoms, molecules, and electromagnetic fields. In particular, ultracold molecules are a promising platform due to their tunable long-range interactions and large set of internal states. However, this nascent platform requires new experimental techniques to create, control, and probe molecular systems.
I will report on efforts to create ultracold polar molecules, coherently manipulate their internal levels, and demonstrate second-scale coherence times in a molecular ensemble. To leverage the long-range, anisotropic dipolar interactions, we engineer dipolar collisions in a bulk ensemble using the technique of microwave dressing. Upon loading polar molecules into a 2D optical lattice, we study dynamics and thermalization in a variety of spin models relevant to quantum magnetism. Toward that end, we develop a novel readout modality – quantum gas microscopy – to perform site-resolved fluorescence imaging, enabling the measurement of quantum correlations and entanglement. The techniques presented here establish ultracold molecules as a compelling platform for quantum science and technology.
Host: Thad Walker
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Department Meeting
CLOSED Department Meeting
Time: 12:15 pm
Place: virtual - link to be sent later.
Speaker: Mark Eriksson, UW-Madison
Closed meeting to discuss personnel matters—pursuant to Section 19.85(1)(c) of the Wisconsin Open Meetings Law.

Closed to all but tenured faculty
Host: Mark Eriksson
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Theory Seminar (High Energy/Cosmology)
New Physics with Gravitational Waves
Time: 1:00 pm
Place: 5280 Chamberlin
Speaker: Jan Schuette-Engel, University of Illinois
Abstract: The thermal plasma in the early universe produced a guaranteed stochastic gravitational wave (GW) background, which peaks today in the microwave regime and was dubbed the cosmic gravitational microwave background (CGMB). I show that the CGMB spectrum encodes fundamental information about particle physics and gravity at ultra high energies. In particular, one can determine from the CGMB spectrum the maximum temperature of the universe and the effective degrees of freedom at the maximum temperature. I point out that quantum gravity effects arise in the CGMB spectrum as corrections to the leading order result. At the end of the talk I discuss detection prospects of the CGMB.
Host: George Wojcik
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