Abstract
We consider type IIA compactification on
K3
. We show that the instanton subsectors of the worldvolume of
N
4-branes wrapped around
K3
lead to a Hagedorn density of BPS states in accord with heterotic-type IIA duality in 6 dimensions. We also find evidence that the correct framework to understand the results of Nakajima on the appearance of affine Kac-Moody algebras on the cohomology of moduli space of instantons on ALE spaces is in the context of heterotic-type IIA string duality.