Path integral derivations of K-theoretic Donaldson invariants
Heeyeon Kim (Rutgers U.)

We discuss path integral derivations of topologically twisted partition functions of 5d SU(2) supersymmetric Yang-Mills theory on M4 x S1, where M4 is a smooth closed four-manifold. Mathematically, they can be identified with the K-theoretic version of the Donaldson invariants. In particular, we provide two different path integral derivations of their wall-crossing formula for b_2^+(M4)=1, first in the so-called U-plane integral approach, and in the perspective of instanton counting. We briefly discuss the generalization to b_2^+(M4)>1.