Globalization of perturbative Chern-Simons theory on the moduli space of flat connections in the BV formalism

Abstract

We study the perturbative path integral of Chern-Simons theory (the effective BV action on zero-modes) in Lorenz gauge, expanded around a (possibly non-acyclic) flat connection, as a family over the smooth irreducible stratum $\mathcal{M}' \subset \mathcal{M}$ of the moduli space of flat connections. We prove that it is horizontal with respect to the Grothendieck connection up to a BV-exact term. From it, we construct a volume form on $\mathcal{M'}$ - the "global partition function" - whose cohomology class is independent of the metric, and so is a 3-manifold invariant. As an element of the construction, we construct an extension of the perturbative partition function to a nonhomogeneous form on the space of triples $(A,A',g)$ consisting of (1) a "kinetic" flat connection $A$ around which Chern-Simons action is expanded, (2) a "gauge-fixing" flat connection $A'$, (3) a metric $g$. This extension is horizontal with respect to an appropriate Gauss-Manin superconnection (which involves the BV operator as a degree zero component).