Vector bundles and $SO(3)$ invariants for elliptic surfaces II: The case of even fiber degree

Abstract

This paper is the second in a series of three devoted to the smooth classification of simply connected elliptic surfaces. In this paper, we study the case where one of the multiple fibers has even multiplicity, and describe the moduli space of stable rank two vector bundles with the appropriate first Chern class needed to calculate Donaldson polynomials. The analysis is in many ways parallel to the analysis in the case of vector bundles of trivial determinant, but the asymmetry between the multiplicities also appears in the moduli space. In this way, the first coefficient of an appropriate Donaldson polynomial determines one of the multiplicities.