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# Events for 11/20/2020 from all calendars

## Student Working Seminar in Groups and Dynamics

## Mathematical Physics and Harmonic Analysis Seminar

## Algebra and Combinatorics Seminar

**Time: ** 11:00AM - 12:00PM

**Location: ** zoom

**Speaker: **Josiah Owens

**Title: ***Schreier Graphs and Schreier Dynamical Systems: "Schreier! Graphin's!" -Gollum, the group theorist*

**Abstract: **The concept of a Schreier graph will be introduced as well as the space of Schreier graphs over a given finitely generated group and its topology. A dynamical system enacted by a group G on a space X (whether topological or measurable) can be isomorphically embedded into the space of Schreier graphs over G or the space of subgroups of G. A given Schreier graph can be associated with a (Schreier) dynamical system, described by its orbit in the space of Schreier graphs over G. We will show that if the action of G on X is minimal, then the orbit of a G-typical Schreier graph is dense in the isomorphic embedding of (G, X) in the space of Schreier graphs.

**Time: ** 1:50PM - 2:50PM

**Location: ** Zoom

**Speaker: **Eduardo Teixeira, University of Central Florida

**Title: ***Shaping diffusion in non-variational models*

**Abstract: **Mathematical models yielding diffusion adjustments are relevant in several fields of research and by now a comprehensive variational theory for treating such problems is well established. The corresponding non-variational theory has been completely open, despite of its potential applicabilities and in this talk I will describe some recent efforts towards launching such a theory. We will introduce a new class of non-divergence form elliptic operators whose degree of degeneracy/singularity varies accordantly to a prescribed power law. Under rather general conditions, we prove viscosity solutions are differentiable, with appropriate (universal) estimates. This result opens a number of new lines of investigation and I'll describe some of these endeavors towards the end of the talk.

**Time: ** 3:00PM - 4:00PM

**Location: ** Zoom

**Speaker: **Pablo Ocal, Texas A&M

**Title: ***Hochschild cohomology of general twisted tensor products*

**Abstract: **The Hochschild cohomology is a tool for studying associative algebras that has a lot of structure: it is a Gerstenhaber algebra. This structure is useful because of its applications in deformation and representation theory, and recently in quantum symmetries. Unfortunately, computing it remains a notoriously difficult task. In this talk we will present techniques that give explicit formulas of the Gerstenhaber algebra structure for general twisted tensor product algebras. This will include an unpretentious introduction to this cohomology and to our objects of interest, as well as the unexpected generality of the techniques. This is joint work with Tekin Karadag, Dustin McPhate, Tolulope Oke, and Sarah Witherspoon.