Seminars are Thursdays at 11am PST in AP&M 6402.
If you are interested in joining the mailing list (or giving a talk), please contact the organizer at jpecamedlin at ucsd dot edu.
October 30, 2025: Rob Webber (UCSD)
Title: How fast is square volume sampling Kaczmarz?
Abstract: Randomized Kaczmarz (RK) is a well-known solver for linear least-squares problems. RK iteratively processes blocks of rows in order to update an approximation to the least-squares solution. Recent work suggests that RK converges rapidly when each block of rows is sampled from the square volume distribution defined by the target matrix. Additionally, there are reports of accelerated convergence when the RK iterates produced in the tail part of the algorithm are averaged together. I will clarify the theoretical convergence guarantees for square volume sampling Kaczmarz both with and without tail-averaging.
November 6, 2025: Andres Contreras Hip (UChicago)
Title: TBD
November 13, 2025: Tom Alberts (University of Utah)
Title: Loewner Dynamics for Real Rational Functions and the SLE(0) Process
Abstract: Recently Peltola and Wang introduced the multiple SLE(0) process as the deterministic limit of the random multiple SLE(kappa) curves as kappa goes to zero. They also showed that the limiting curves have important geometric characterizations that are independent of their relation to SLE(kappa) - they are the real locus of real rational functions, and they can be generated by a deterministic Loewner evolution driven by multiple points. We prove that the Loewner evolution is a very special family of commuting SLE(0, rho) processes (with commutation holding in a very strong sense), and use this to directly show that the curves satisfy a geodesic multichord property. We also show that our SLE(0, rho) processes lead to relatively simple solutions for the degenerate versions of the BPZ equations in terms of the poles and critical points of the rational function, and that the dynamics of these poles and critical points come from the Calogero-Moser integrable system. Although our results are purely deterministic they are again motivated by taking limits of probabilistic constructions in conformal field theory. Joint work with Sung-Soo Byun, Nam-Gyu Kang, and Nikolai Makarov.
November 20, 2025: Brian Hall (Notre Dame)
Title: TBD
December 4, 2025: Kevin Ren (Princeton)
Title: TBD
January 15, 2026: Guillaume Blanc (EPFL)
Title: TBD
January 29, 2026: Yujin Kim (Caltech)
Title: TBD
October 16, 2025: Yubo Shuai (UCSD)
Title: The site frequency spectrum in population models
Abstract: The site frequency spectrum is a commonly used statistic to summarize the mutational data in a sample from the population. In this talk, we will consider the site frequency spectrum for populations growing exponentially or under spatial constraints. I will also briefly discuss some applications to biological data.
October 2, 2025: Benedikt Stufler (TU Vienna)
Title: Inhomogeneous scaling limits of random supertrees.
Abstract: We discuss recent results on Gibbs partitions and their application to the study of random supertrees and their novel inhomogeneous scaling limits.
September 11, 2025: Ron Nissim (MIT) (**AP&M 7321**)
Title: Area Law for Lattice Yang-Mills at Strong Coupling
Abstract: This talk is based on joint work with Scott Sheffield and Sky Cao on lattice Yang-Mills theory. Yang-Mills theory is the mathematical model for the standard model of particle physics, and the area law is the property of the Yang-Mills model said to explain the physical phenomenon of quark confinement. The lattice Yang-Mills model assigns a random NxN matrix from classical Lie groups such as U(N), SU(N), or SO(N) to each edge of a lattice. An adjustable parameter of the model, beta, sometimes referred to as "inverse temperature" describes the coupling strength of the model. It is generally believed that the lattice Yang-Mills model greatly simplifies when beta is proportional to N and N gets large, and in the N->infinity limit under this scaling, area law is known to hold. Nevertheless, for finite N the area law was only shown for beta < c_d/N for a dimensional constant c_d prior to our work (a regime of beta which gets smaller as N gets large!). In a recent preprint we use a novel surface exploration point of view to increase the range of parameters to beta < c_d independent of N, and in ongoing work we use the dynamical perspective introduced by Shen, Zhu, and Zhu to further improve the regime to beta < c_d N which is the scaling of the previously mentioned large N limit of the model. Both of these approaches work for any dimension of the lattice, d. Introducing these two approaches to the area law question will be the goal of the talk.
Previous seminar talks from 2024-2025 are found here