Events at Physics |
Events During the Week of April 26th through May 3rd, 2026
Monday, April 27th, 2026
- Theory Seminar (High Energy/Cosmology)
- No Shift, Sherlock: No Shift Symmetries in AdS/CFT
- Time: 1:00 pm - 2:30 pm
- Place: Chamberlin 5280
- Speaker: José Calderón-Infante, Caltech
- Abstract: The absence of global symmetries is a long-standing conjecture about quantum gravity. In this talk, I will focus on continuous global shift symmetries in AdS/CFT, with the goal of developing a CFT-based argument against them. First, I will discuss how a shift symmetry in the bulk is reflected on the boundary CFT. This raises the question of whether local, unitary CFT can exhibit such property. I will present an argument that, under a certain assumption, rules out this possibility. Then, I will introduce some CFTs that do not satisfy this assumption and argue that this leads to an exotic type of shift symmetry gauging in the bulk. A key role will be played by the CFT stress tensor, which is dual to the graviton in the bulk. To see how theories without gravity avoid our argument, I will describe how it fails in the boundary theory of a massless free scalar in AdS, namely the generalized free field theory of a marginal operator. Finally, if time permits, I will address whether this type of argument could lead to a bound on how much the shift symmetry must be broken.
- Host: Gary Shiu
Tuesday, April 28th, 2026
- Preliminary Exam
- Large Language Models for Theoretical Physics and Cosmology: Benchmarking Reasoning, Scaling Inference, and Discovering Scientific Algorithms
- Time: 9:00 am - 11:00 am
- Place: 3290 Chamberlin
- Speaker: Tianyi Li, Physics PhD Graduate Student
- Abstract: This presentation explores the application of Large Language Models (LLMs) in theoretical physics and computational cosmology across three key frontiers: evaluation, inference optimization, and algorithmic discovery. First, we introduce the Theoretical Physics Benchmark (TPBench) to assess LLM reasoning, demonstrating that while foundational models are advancing, research-level physics remains a critical bottleneck. To address these reasoning limits, we investigate test-time scaling techniques. We propose a novel symbolic weak-verifier that exploits the intrinsic mathematical structure of physics problems, significantly outperforming standard scaling methods. Finally, we introduce MadEvolve, an evolutionary optimization framework that transitions LLMs from solving established problems to discovering novel scientific methods. By autonomously generating and refining code, MadEvolve yields improved algorithms for complex cosmological tasks such as initial condition reconstruction and 21cm foreground mitigation. Together, these works outline a concrete pathway for leveraging LLMs to accelerate autonomous discovery in physics.
- Host: Moritz Münchmeyer
- Council Meeting
- Time: 3:00 pm - 4:00 pm
- Place: 2314 Chamberlin
- Speaker: Kevin Black
- Host: Kevin Black
Wednesday, April 29th, 2026
- Department Meeting
- Time: 12:15 pm - 1:15 pm
- Place: B343 Sterling
- Speaker: Kevin Black, UW - Madison, Department of Physics
- Department Meeting
- Host: Kevin Black
- Astronomy Colloquium
- Whitford Public Talk: The Mysteries of Cosmic Dust
- Time: 7:00 pm - 8:30 pm
- Place: 1310 Sterling Hall
- Speaker: Bruce Draine, Princeton University
- Abstract: The first galaxies form stars out of initially pristine gas. After a
few million years the gas is enriched with heavy elements formed by
the first generation of stars. Dust starts to appear in small
amounts, and H2 formation by catalysis on dust grains begins.
JWST Spectroscopy of I Zw 18, a very metal-poor star-forming galaxy in
the nearby universe, provides an opportunity to study these
beginnings. The composition of the first dust is found to be very
different from dust in a mature galaxy such as the Milky Way. The
molecular hydrogen emission spectrum allows the ortho/para ratio to be
determined, with the ortho/para ratio found to exceed 3 in some regions.
Implications will be discussed. Thursday, April 30th, 2026
- R. G. Herb Condensed Matter Seminar
- A universal model of Floquet operator Krylov Space
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Aditi Mitra, NYU
- Abstract: It is shown that the stroboscopic time-evolution under a Floquet unitary, in any spatial dimension, and of any Hermitian operator, can be mapped to an operator Krylov space which is identical to that generated by the edge operator of the non-interacting Floquet transverse-field Ising model (TFIM) in one-spatial dimension, and with inhomogeneous Ising and transverse field couplings. The latter has four topological phases reflected by the absence (topologically trivial) or presence (topologically non-trivial) of edge modes. It is shown that the Floquet dynamics share certain universal features characterized by how the Krylov parameters vary in the topological phase diagram of the Floquet TFIM with homogeneous couplings. Connections of our results with methods based on orthogonal polynomials on the unit circle are discussed. Applications to slow dynamics of quasi-conserved quantities as well as Anderson localization and the localization-delocalization transition are presented.
- Host: Elio König
- Preliminary Exam
- Measurement of the Neutrino Flux from the Milky Way using the IceCube Multi-Flavor Astrophysical Neutrino Sample
- Time: 2:30 pm - 4:00 pm
- Place: 5280 CH
- Speaker: Matthias Thiesmeyer, Physics PhD Graduate Student
- Abstract: The IceCube Neutrino Observatory has provided new insights into the high-energy universe, unveiling neutrinos from the galactic plane to extragalactic supermassive black holes. In this talk, we present a 12.3-year, full-sky, all-flavor dataset, the IceCube Multi-Flavor Astrophysics Neutrino sample (ICEMAN). ICEMAN is the combination of three largely independent neutrino samples of different event morphologies. It builds upon the previous work of the DNN-based cascade sample, Enhanced Starting Track Event Selection, and the Northern Track sample. Recent improvements in ice modeling and detector calibration are also incorporated into the cascade simulation and reconstruction. This dataset was used in an unbinned maximum likelihood to carry out a template-based measurement of the diffuse galactic neutrino flux across four distinct model hypotheses. Preliminary measurement results will be presented, addressing the different model assumptions. Furthermore, prospects of a follow-up analysis targeting the galactic center using enhancements in background simulation will be discussed.
- Host: Lu Lu
- Astronomy Colloquium
- Whitford Lecture: Dust and Molecular Hydrogen in a galaxy with 3% Solar abundances
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Prof. Bruce Draine, Princeton University
- Abstract: The first galaxies form stars out of initially pristine gas. After a few million years the gas is enriched with heavy elements formed by the first generation of stars. Dust starts to appear in small amounts, and H2 formation by catalysis on dust grains begins. JWST Spectroscopy of I Zw 18, a very metal-poor star-forming galaxy in the nearby universe, provides an opportunity to study these beginnings. The composition of the first dust is found to be very different from dust in a mature galaxy such as the Milky Way. The molecular hydrogen emission spectrum allows the ortho/para ratio to be determined, with the ortho/para ratio found to exceed 3 in some regions. Implications will be discussed.
- Host: Nicholas Stone
Friday, May 1st, 2026
- Academic Calendar
- Last Class Day
- Abstract: *Note: actual end time may vary.* CONTACT: admin@secfac.wisc.edu
- Thesis Defense
- Taking Inventory of the Most Promising Lensed Radio Sources for Constraining Fundamental Properties of Dark Matter
- Time: 12:00 pm - 2:00 pm
- Place: 5280 Chamberlin or
- Speaker: Michael Martinez, Physics PhD Graduate Student
- Abstract: While Dark Matter (DM) makes up roughly 80% of the total matter in the Universe, its microscopic properties remain one of the biggest questions in Cosmology today. Fortunately, those properties dictate the distribution and form of macro-scale gravitational structures in the universe, allowing for indirect studies which can distinguish between competing particle models. One such avenue for this research is via strong gravitational lensing systems, where dark halos in the lens substructure and along the line of sight perturb image positions and flux. However, the current population of sources suitable for this analysis is limited, especially at radio wavelengths where astrometric perturbations are observable. I will first discuss which properties of lens systems make them especially useful for DM constraints and examine the minimum amount of information necessary for such an experiment. Then, I present the results of two successful searches for new radio lenses in existing radio and optical surveys, utilizing a new method to expand the potential follow-up population for Dark Matter studies in the future. I conclude with a discussion of the completeness of this population.
- Host: Keith Bechtol
- Physics Department Colloquium
- Building a quantum computer out of single photons and single atoms
- Time: 2:00 pm - 3:00 pm
- Place: Chamberlin 2241 -
- Speaker: Josiah Sinclair, Carl & Brynn Anderson Assistant Professor of Physics, UW - Madison
- Abstract: Investiture lecture for the Assistant Professor Josiah Sinclair as the Carl and Brynn Anderson Professor of Physics
- Host: Mark Saffman
- Preliminary Exam
- Modelling Nonequilibrium Superconducting Dynamics for MKID Applications
- Time: 3:00 pm - 5:00 pm
- Place: 4272 Chamberlin
- Speaker: Soren Ormseth, Physics PhD Graduate Student
- Abstract: Microwave Kinetic Inductance Detectors (MKIDs) are a leading-edge technology for the high-precision detection of single photons across the electromagnetic spectrum, from the far-infrared to X-rays. While their macroscopic operating principle, photon-induced shifts in kinetic inductance, is well understood, current models often rely on equilibrium approximations that fail to capture the complex, non-thermal dynamics of quasiparticles and phonons. This gap limits our ability to optimize MKID sensitivity and resolving power. Here, we present a modeling framework for nonequilibrium superconducting physics that accounts for quasiparticle and phonon spatial transport and scattering. By resolving these dynamics, this model provides a pathway to understanding operational behaviors in MKIDs such as pulse-shape variations or readout-induced noise. Furthermore, the universality of this approach is applicable to the problem of quasiparticle poisoning in superconducting qubits, and we aim to provide a unified tool for advancing the performance of next-generation superconducting quantum devices."
- Host: Peter Timbie
- Physics Department Colloquium
- Anderson, Lawler, Lin annual Lecture (inaugural)
- Aerosol Nexus in the Stratosphere
- Time: 3:30 pm - 4:30 pm
- Place: 2241 Chamberlin Hall -
- Speaker: David Fahey, NOAA, Director of the Chemical Sciences Laboratory
- Abstract: Stratospheric aerosols play a central role in Earth's radiative balance and atmospheric chemistry. A variety of sources both natural and anthropogenic influence the background aerosol abundance and cause extreme events. Important examples are volcanic eruptions, space traffic and wildfires. Understanding this central role requires a focus on a variety of sources with stratospheric observations and modeling studies that include chemistry, composition, microphysics, radiation and transport; hence the aerosol nexus. Initiated by Congressional mandate, NOAA’s Earth Radiation Budget (ERB) program was established to study aerosol sources and aerosol processes in the troposphere and stratosphere. ERB includes stratospheric aerosol injection (SAI)—the concept of increasing Earth’s albedo by enhancing stratospheric aerosol—which is emerging internationally as a pressing, albeit controversial, research priority. The Chemical Sciences Laboratory is pursuing fundamental research related to stratospheric aerosols through innovative instrumentation, platform use, observations and modeling, supported in part by the ERB program. I will provide some context to the program and present selected research highlights, including the role of SAI in the Montreal Protocol Scientific Assessment of Ozone Depletion. I am honored in giving this presentation because the guidance and mentoring I received from Professors Anderson, Lawler and Lin, and the Physics Department, had exceptional influence in my formative years.
- Host: Thad Walker
- Physics Department Awards Banquet
- Time: 5:30 pm - 9:00 pm
- Place: Wisconsin Institute for Discovery
- Host: Kevin Black
Saturday, May 2nd, 2026
- Academic Calendar
- Study Day
- Abstract: *Note: actual end time may vary.* CONTACT: admin@secfac.wisc.edu
Sunday, May 3rd, 2026
- Academic Calendar
- Exams Begin
- Abstract: *Note: actual end time may vary.* CONTACT: admin@secfac.wisc.edu