Events at Physics |
Events on 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
- Modelling Nonequilibrium Superconducting Dynamics for MKID Applications
- Time: 11:00 am - 1:00 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
- 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