Events for 10/23/2019 from all calendars

Student Working Seminar in Groups and Dynamics

Time: 1:00PM - 2:00PM

Location: BLOC 628

Speaker: Nóra Gabriella Szőke, Institut Fourier

Title: Extensive Amenability

Abstract: A group action is called amenable if there exists an invariant mean on the space. In this talk I will present a stronger property, namely the extensive amenability of group actions. This property was introduced by Juschenko and Monod, they used it to construct the first examples of finitely generated infinite amenable simple groups. We will discuss some properties of extensive amenability and see an application for topological full groups.

Number Theory Seminar

Time: 1:45PM - 2:45PM

Location: BLOC 220

Speaker: Changningphaabi Namoijam, Texas A&M University

Title: Hyperderivatives of Periods and Logarithms of A Drinfeld Module, and Their Algebraic Relations

Abstract: In 2012, Chang and Papanikolas showed algebraic independence of periods, quasi-periods, certain logarithms and quasi-logarithms of Drinfeld modules. Using Papanikolas’ results on transcendence degree of the period matrix of a t-motive and dimension of its Galois group, we determine algebraic relations among hyperderivatives of periods, quasiperiods, logarithms and quasi-logarithms of Drinfeld modules.

Noncommutative Geometry Seminar

Time: 2:00PM - 3:00PM

Location: BLOC 628

Speaker: Rufus Willett, University of Hawai'i

Title: Decompositions and K-theory

Abstract: We introduce a notion of 'local decomposability' for a C*-algebra, inspired by the theory of nuclear dimension (due to Winter and Zacharias) and of dynamical complexity (due to Guentner, Yu and the speaker). We derive the existence of a sort-of controlled Mayer-Vietoris sequence in this setting, inspired by work of Oyono-Oyono and Yu in controlled K-theory (although not using that language), and give applications to Baum-Connes theory and to the Künneth formula.

Groups and Dynamics Seminar

Time: 3:00PM - 4:00PM

Location: BLOC 220

Speaker: Nóra Gabriella Szőke

Title: A Tits alternative for topological full groups

Abstract: I will present a Tits alternative for topological full groups of minimal actions of finitely generated groups. On the one hand, the topological full group of a minimal action of a virtually cyclic group is amenable. This is a generalization of the result of Juschenko and Monod for Z-actions. On the other hand, when a finitely generated group G is not virtually cyclic, then we can construct a minimal free action of G on a Cantor space such that the topological full group contains a non-abelian free group.

Graduate Student Organization Seminar

Time: 4:00PM - 5:00PM

Location: BLOC 628

Speaker: John Weeks

Title: Bass-Serre Theory: Why Graphs and Groups Go Together

Abstract: We discuss from first principles the definitions of amalgamated free product from algebra and trees from graph theory. We then give an intuitive description of how trees and certain elementary amalgamated free products are in one-to-one correspondence. This talk will be light on proof and heavy on beauty.