Instanton counting: the K-theoretic partition function -- Hiraku Nakajima

I will explain my paper math.AG/0505553 with Yoshioka. We study the K-theoretic version of Nekrasov's partition function, which is the generating function of the character of the coordinate rings of moduli spaces of instantons on R^4. It is conjecturally related to the K-theoretic Donaldson invariants.