**
Stefan Mendez-Diez
**

**K-theoretic Aspects of String Theory
Dualities
**

**Abstract
**

This talk will discuss K-theoretic matching of D-brane charges in the string duality between the type I superstring theory on a 4-torus and the type IIA theory on a K3 surface. We will see that replacing K3 by its orbifold blow-down seems to resolve many of the apparent problems that arise in the theory from using a smooth K3, such as not having an isomorphism of the torsion charges. We will also discuss how using the equivariant K-theory classification of D-brane charges on the orbifold limit of K3 provides added information about the K-theory of the blow-down.