Math Colloquia

If you are interested in giving a talk, please email Dr. Daniel Vallieres (dvallieres@csuchico.edu).

Colloquia are typically held on Friday in Holt 175. Please see below for specific information. Refreshments are served at 3:45 p.m. and the talk begins at 4:00 p.m. Everyone is invited to attend!

Spring 2026

• April 17 — Alison Tatsuoka, Princeton University
  
  Title: Barbells and knotted things
  Abstract: There are many interesting ways that a circle can live in 3-dimensional space; these are called knots, and have been studied by mathematicians since the late 1700s (and by artists, sailors, druids, and shoelace-tyers since long before...). There are also many interesting ways that a 2-dimensional sphere can live in 4-dimensional space; these are called 2- knots, the study of which was initiated by Artin in 1925. Many nice properties enjoyed by circles in 3-space fall apart for 2-spheres in 4-space. We’ll describe a couple of these properties, and outline some constructions that show how they fail in dimension 4. The main tool we’ll use is barbell diffeomorphisms, which were introduced by Budney-Gabai in 2019; we’ll describe what these are as well.
  
  
• April 10 — Juhee Lee, UC Santa Cruz 
  
  Title: Utility-Based Statistical Decision-Making with Multivariate Outcomes in Clinical Trials and Personalized Treatment
  
  Abstract: I will discuss statistical methods for decision-making in clinical trials that explicitly account for trade-offs between treatment efficacy and safety. The key idea is to use elicited utility functions to quantify how desirable different patient outcomes are.
  
  First, I consider randomized clinical trials in which each patient has both an efficacy and a safety outcome. By assigning numerical utilities to all possible outcome combinations, treatments can be compared through their average utility. This leads to a simple testing procedure that incorporates both benefits and risks, providing a practical alternative to a non-inferiority test that is based on efficacy alone, relies on the implicit assumption that the experimental treatment is safer than the control.
  Second, I present a Bayesian approach for personalized treatment selection based on data from randomized trials. Here, utilities may depend on patient characteristics, allowing treatment decisions to reflect individual preferences and risk profiles. The method employs a Bayesian nonparametric regression model to flexibly model and accurately predict outcomes, thereby enabling selection of the treatment that maximizes expected utility for each patient. An application to a breast cancer trial illustrates how the preferred treatment can vary with age due to differences in tolerance for toxicity.
  Together, these approaches provide a unified framework for incorporating clinically meaningful trade-offs into both trial design and individualized treatment decisions.
  
  Joint work with: Peter F. Thall (Department of Biostatistics, UT M.D. Anderson Cancer Center, Houston, TX), Bora Lim (Department of Breast Medical Oncology, UT M.D. Anderson Cancer Center, TX, U.S.A), Pavlos Msaouel (Departments of Genitourinary Medical Oncology and Translational Molecular Pathology, UT M.D. Anderson Cancer Center, Houston, TX)
  
  

• Mar. 13 — Florian Sprung, Arizona State University
  
  Title: Iwasawa Theory: Bridging Algebra and Analysis
  Abstract: Iwasawa theory connects algebra and analysis in the context of the p-adic topology. The main purpose of this talk is to give a flavor of what Iwasawa theory is about, in particular the Iwasawa theory of number fields. I will also sketch some of the generalizations, and if time permits, I will report on recent progress concerning the Iwasawa theory of motives (joint with Jishnu Ray).

• Feb. 27 — Rusiru Gambheera, UC Santa Barbara

Fall 2025

• Sept. 26 — Matt Krauel, CSU Sacramento
• Oct. 3 — Lew Ludwig, Denison Univ.
• Oct. 17 — Edgar A Bering IV, San Jose State
• Oct. 31 — Jie Peng, UC Davis
• Nov. 7 — Edward Roualdes, Chico State
• Nov. 21 — Marcus Battraw, Chico State
• Dec. 12 — Vardayani Ratti, CSU Sacramento