Guenther Trautmann (Kaiserslautern)
Title: Algebraic Bubbling for Degenerations of Vector Bundles on Surfaces
Abstract: In Differential Geometry degenerations of Yang-Mills fields
have been described by bubbling of 4-spheres by Taubes and Uhlenbeck.
It turned out that a similar process in algebraic geometry exists.
Sheaves on surfaces which are limits of vector bundles can be replaced
by vector bundles on trees of surfaces under appropriate processes
of blowing up. The result is the construction of complete moduli spaces of
bundles on trees of surfaces which are birational to the Gieseker-Maruyama
compactifications.