Instantons in topological field theories

Abstract

On an oriented, compact, connected, real four-dimensional manifold, $M$, we introduce a topological Lagrangian gauge field theory with a Bogomol'nyi structure that leads to non-singular, finite-Action, stable solutions to the variational field equations. These soliton-like solutions are analogous to the instanton in Yang-Mills theory. Unlike Yang-Mills instantons, however, `topological' instantons are independent of any underlying metric structure, and, in particular, they are independent of the metric signature. We show that when the topology of the underlying manifold, $M$, is equipped with a complex K\"ahler structure, and $M$ is interpreted as space-time, then the moduli space of topological instantons---the space of motions---is a finite-dimensional, smooth, Hausdorff manifold with a natural symplectic structure. We identify space-time topologies which lead to the physical stability of topological instanton field configurations compatible with the additional geometric structures. The spaces of motion for $U(1)$ topological instantons over either minimal elliptic or algebraic complex space-times with irregularity $q=2$ are examined.