Representability for some moduli stacks of framed sheaves

Abstract

We prove a representability theorem for moduli functors of framed torsion-free sheaves on nonsingular complex projective surfaces, using formal geometry along a curve in the surface. This has as a consequence that a certain restriction morphism for moduli stacks of sheaves has fibers that are schemes.

6 pages, AMSLaTeX, substantially revised and shortened version