On symplectic 4-manifolds with prescribed fundamental group

Abstract

In this article we study the problem of minimizing $aχ+bσ$ on the class of all symplectic 4--manifolds with prescribed fundamental group $G$ ($χ$ is the Euler characteristic, $σ$ is the signature, and $a,b\in \BR$), focusing on the important cases $χ$, $χ+σ$ and $2χ+3σ$. In certain situations we can derive lower bounds for these functions and describe symplectic 4-manifolds which are minimizers. We derive an upper bound for the minimum of $χ$ and $χ+σ$ in terms of the presentation of $G$.

30 pages, 4 figures. New Version: Added examples covering free abelian groups with odd rank