# Events for 06/10/2020 from all calendars

## Groups and Dynamics Seminar

**Time: ** 12:00PM - 1:00PM

**Location: ** 940 9667 3668

**Speaker: **Mark Sapir, Vanderbilt U.

**Title: ***Groups with quadratic Dehn function and undecidable conjugacy problem*

**Abstract: **This is a joint work with A. Yu. Olshanskii. We construct a finitely
presented group with quadratic Dehn function and undecidable conjugacy
problem. This solves a problem of E. Rips. We also prove that our
group has decidable power conjugacy problem. So it is the first
example of a group with decidable word and power conjugacy problems
and undecidable conjugacy problem.

## Noncommutative Geometry Seminar

**Time: ** 1:00PM - 2:00PM

**Location: ** Zoom 942810031

**Speaker: **Jianchao Wu, Texas A&M University

**Title: ***The Novikov conjecture and C*-algebras of infinite dimensional nonpositively curved spaces*

**Abstract: **The rational strong Novikov conjecture is a prominent problem in noncommutative geometry. It implies deep conjectures in topology and differential geometry such as the (classical) Novikov conjecture on higher signatures and the Gromov-Lawson conjecture on positive scalar curvature. Using C*-algebraic and K-theoretic tools, we prove that this conjecture holds for any discrete group admitting an isometric and proper action on a (possibly infinite-dimensional) nonpositively curved space that we call an admissible Hilbert-Hadamard space, partially extending earlier results of Kasparov and Higson-Kasparov. In particular, our result can be applied to geometrically discrete subgroups of the group of volume preserving diffeomorphisms of a closed smooth manifold, as they act on an infinite-dimensional symmetric space called the space of L^2-Riemannian metrics. A crucial ingredient of our proof is the construction of C*-algebras from infinite dimensional nonpositively curved spaces. This is joint work with Sherry Gong and Guoliang Yu.

**URL: ***Event link*