# Math Calendar

### Upcoming Events

## Topology & Group Theory Seminar

## The global shape of universal covers- Virtual Talk — On Zoom

Sergio Zamora Barrera (Penn State)

Topology & Group Theory Seminar page for Zoom meeting information

If one starts with the universal cover of a compact space, and looks at it from very far, what would the limiting shape be? It is well known (Gromov-Pansu Theorem) that if there is a limiting shape, then it must be a Carnot-Carathéodory group; a simply connected nilpotent Lie group with a special type of invariant metric.

I will talk about the similar problem of studying the limit shapes of universal covers of sequences of spaces shrinking to a point.

## Joint Vanderbilt/MTSU Graph Theory and Combinatorics Seminar-Minimal quadrangulations of surfaces-SC1308

Mark Ellingham, Vanderbilt University

Zoom link https://vanderbilt.zoom.us/j/92800454642

The meeting ID is 928 0045 4642.

Abstract: A minimal quadrangulation of a surface is a quadrangular (every face is bounded by a 4-cycle) embedding of a (simple) graph in a surface, such that no graph with fewer vertices has a quadrangular embedding in that surface. These include quadrangular embeddings of complete graphs, which provide sharpness examples for a strengthening of the Map Colour Theorem. We determine the number of vertices of a minimal quadrangulation for all connected compact surfaces, using a technique originally due to Hartsfield, which we call the “diagonal technique”. This is joint work with Wenzhong Liu and Dong Ye

## Subfactor Seminar

## Miscellaneous about Commutants mod

Dan-Virgil Voiculescu, UC Berkeley

Zoom ID 94393956397 Subfactor Seminar page for Zoom meeting information

I will discuss some general aspects of commutants modulo normed ideals. This will include iteration of the construction, the commutant mod associated with a smooth manifold and an analogy with capacity in nonlinear potential theory.

## Dissertation Defense-New examples of irreducible subfactors of the hyperfinitte II_1 factor with rational, non-integer index

Hrvoje Stojanovic, Vanderbilt University

https://vanderbilt.zoom.us/j/99140969389

## Qualifying Exam – Some Optimal Periodic Configurations-SC1 1313

Nate Tenpas, Vanderbilt University

## Topology & Group Theory Seminar

## S-Machines can emulate Turing machines in quasilinear time.

Bogdan Chornomaz (Vanderbilt)

Topology & Group Theory Seminar page for Zoom meeting information

S-machines were first introduced in a 1997 paper (published only in 2002) by Sapir, Birget, and Rips, where they were used to prove that a finitely generated group G with a word problem of complexity T(n) can be embedded into a finitely presented group H with Dehn function of G in H at most T(n)4. This bound hinges on the fact that S-machine can emulate a Turing machine in time T(n)3. We improve this emulation bound to T(n)1+ε for any ε>0, which, hopefully, implies that the bound on the Dehn function can be improved to T(n)2+ε.

## Dissertation Defense-Growth Of Dehn Twist and Pseudo-Anosov Conjugacy Classes in Teichmüller Space- Location: SC1312

Jiawei Han, Vanderbilt University

## Subfactor Seminar

## Irreducible inclusions of simple C*-algebras

Mikael Rordam, University of Copenhagen

Zoom ID 94393956397 Subfactor Seminar page for Zoom meeting information

There are several naturally occurring interesting examples of inclusions of simple C*-algebras with the property that all intermediate C*-algebras likewise are simple. By an analogy to von Neumann algebras, we refer to such inclusions as being C*-irreducible. We give an intrinsic characterization of C*-irreducible inclusions, and use this characterization to exhibit (and revisit) such inclusions, both known ones and new ones, arising from groups and dynamical systems. By a theorem of Popa, an inclusion of II_1-factors is C*-irreducible if and only if it is irreducible with finite Jones index. We explain how one can construct C*-irreducible inclusions from inductive limits. In a recent joint work with Echterhoff we consider when inclusions of the form $A^H \subseteq A \rtimes G$ are C*-irreducible, where G and H are groups acting on a C*-algebra A. Such inclusions in the setting of II_1 factors were considered by Bisch and Haagerup.

## PDE Seminar

## PDE-Seminar- Title- TBD

Katrina Morgan, Northwestern University

PDE Seminar page for Zoom meeting information

## Computational Analysis Seminar

## Computational Analysis- Title- TBD

Alex Cloninger, University of California – San Diego

Computational Analysis Seminar page for Zoom meeting information

## Subfactor Seminar

## Subfactor Seminar- Title TBD

Changying Ding, Vanderbilt University

Zoom ID 94393956397 Subfactor Seminar page for Zoom meeting information

## Computational Analysis Seminar

## Computational Analysis- Title TBD

Bernhard Bodmann, University of Houston

Computational Analysis Seminar page for Zoom meeting information

## PDE Seminar

## PDE Seminar- Title- TBD

Federico Pasqualotto, Duke University

PDE Seminar

## PDE Seminar

## PDE- Title- TBD

Federico Pasqualotto, Duke University

PDE Seminar page for Zoom meeting information

## Subfactor Seminar

## Subfactor Seminar- Title TBD

Corey Jones, North Carolina State University

Zoom ID 94393956397 Subfactor Seminar page for Zoom meeting information

## Computational Analysis Seminar

## Computational Analysis- Title- TBD

Yvonne Ou, University of Delaware

Computational Analysis Seminar page for Zoom meeting information

## Subfactor Seminar

## Subfactor Seminar- Title- TBD

Sorin Popa, UCLA

Subfactor Seminar page for Zoom meeting information Zoom ID 94393956397

## Computational Analysis Seminar

## Computational Analysis- Title TBD

Peter Hinow, University of Wisconsin, Milwaukee

Computational Analysis Seminar page for Zoom meeting information

## PDE Seminar

## PDE- Title TBD

Ákos Nagy, UC Santa Barbara

PDE Seminar page for Zoom meeting information

## Subfactor Seminar

## Subfactor Seminar- Title TBD

James Tener, ANU Mathematical Sciences Institute

Zoom ID 94393956397 Subfactor Seminar page for Zoom meeting information