Globalization of perturbative Chern-Simons theory on the moduli space of flat connections in the BV formalism
Pavel Mnev, Konstantin Wernli
TL;DR
This work develops a BV-formalism framework for perturbative Chern-Simons theory around non-acyclic flat connections on a closed 3-manifold, organizing the analysis via the smooth irreducible moduli stratum $\mathcal M'$. It introduces desynchronized perturbative data and a Gauss-Manin/Grothendieck-connection formalism to achieve horizontality across families of flat connections and gauge-fixing choices. By extending the perturbative partition function to nonhomogeneous forms and implementing metric-renormalization, the authors construct a global volume form $Z^{\mathrm{glob}}$ on $\mathcal M'$, whose cohomology class is metric-independent and yields a framed 3-manifold invariant upon integration over components. The theory is supplemented by a detailed formal geometry of the moduli space, a perturbative-dQME framework, and a motivating $\\Sigma\times S^1$ example that aligns with Reshetikhin–Turaev invariants in the large level limit. Overall, the paper provides a rigorous route from local perturbative data to global, metric-insensitive invariants arising from 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).
