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

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I will explain my paper 
<a href=http://arxiv.org/abs/math/?0505553>math.AG/0505553</a> 
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.