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Department of Mathematics

Upcoming Events

Branwen Purdy at her stall during OMSI meet-a-scientist day.

Branwen Purdy prepares hands-on activities for kids at the OMSI Meet-A-Scientist Day in Portland, to share hands-on learning experiences about her research in topological data analysis.

Join us for these events hosted by the Department of Mathematics, including colloquia, seminars, graduate student defenses and outreach, or of interest to Mathematicians hosted by other groups on campus.

Access our archive of events

Polynomials from random walks: accelerating the non-symmetric power iteration

STAG 112
Applied Mathematics and Computation Seminar

Speaker: Peter Cowal

ABSTRACT: In numerical linear algebra, an iterative method that alternates between applying a matrix and taking linear combinations of the result corresponds to applying a polynomial to a matrix. The action of the polynomial on the eigenvalues of the matrix determines the output of the method. In this talk, we'll present a class of polynomial families based on mean-zero random walks which are closely related to Faber polynomials, with useful boundedness and rapid-growth properties on the complex plane. Additionally, we'll present a momentum-based acceleration scheme for the power iteration that significantly outperforms the power iteration for certain classes of non-symmetric matrices with small spectral gaps.This talk is based on joint work with Nicholas Marshall and Sara Pollock. Read more.

Maximal Symplectic Torus Actions

Kidder Hall 238 and zoom
Geometry and Topology Seminar

Speaker: Rei Henigman

Abstract:Let a torus act smoothly on a smooth manifold. Informally, the action is (isotropy) maximal if it cannot be extended locally to a higher-dimensional action. For Riemannian manifolds, maximal isometric torus actions were classified by Escher and Searle. In this talk, we will discuss a similar result for actions on symplectic manifolds, which preserve the symplectic form. To be precise, we give a complete classification of maximal symplectic torus actions on symplectic manifolds. We will not assume any familiarity with symplectic geometry. Please email Sergio Zamora ([email protected]) for the zoom link. Read more.