We will talk about Kronheimer and Mrowka’s knot concordance invariant, $s^\sharp$. We compute the invariant for various knots. Our computations reveal some unexpected phenomena, including that $s^\sharp$ differs from Rasmussen's invariant $s$, and that it is not additive under connected sums. We also generalize the definition of $s^\sharp$ to links by giving a new characterization of the invariant in terms of immersed cobordisms.

Exhaustive representations were introduced by Nistor and Prudhon, motivated by characterizations of Fredholm operators and spectral theory of N-body Hamiltonians. Coarse geometry deals with the geometry at infinity of metric spaces with bounded geometry via the Roe algebra. In particular, Spakula and Willlett show how to construct a family of representations of the Roe algebra which can be thought of "the representations at infinity". We will be studying when this family is exhaustive. This is joint work with Yu Qiao.

Noncommutative geometry provides a potent approach to the study of the algebraic geometry (e.g., K-theory) of infinite dimensional manifolds. In this talk, I will outline the construction of C*-algebras associated to Hilbert-Hadamard spaces, understood as a kind of (typically infinite dimensional) nonpositively curved manifolds. Under mild assumptions, these C*-algebras retain a remnant of Bott periodicity, which we exploit to prove the Novikov conjecture of geometrically discrete groups of diffeomorphisms. This is joint work with Sherry Gong and Guoliang Yu.

TBA