From multiplicative to additive geometry: Deformation theory and 2D TQFT

TL;DR

This paper develops a deformation theory connecting multiplicative and additive geometries, extending to singular cases, and constructs a 2D topological quantum field theory based on quasi-Hamiltonian manifolds, with applications to moduli spaces.

Contribution

It introduces a generalized Hamiltonian deformation theory for singular cases and constructs a 2D TQFT using quasi-Hamiltonian spaces, linking geometry and quantum field theory.

Findings

Deformation from double D(G) to cotangent bundle T*G in singular cases.

Construction of a 2D TQFT invariant under quiver homotopy.

Quasi-Hamiltonian spaces associated to cobordisms via fusion product.

Abstract

In this paper, we present a theory of Poisson deformation of Hamiltonian quasi-Poisson manifolds to Hamiltonian Poisson manifolds that include degenerate cases. More significantly, this theory extends to singular cases arising from symplectic implosion: we introduce a generalized Hamiltonian deformation theory and we show that the imploded cross section of the double $D(G)_\imp$ deforms to the implosion of the cotangent bundle $T^*G_\imp$ with applications to the master moduli space of $G$-flat connections.\\ In parallel, we construct a topological quantum field theory $\N: \text{Cob}_{2}\to \mathbf{QHam}$, where $\mathbf{QHam}$ is the category of quasi-Hamiltonian manifolds. To each cobordism $\Sigma$, we associate a quasi-Hamiltonian space $\N(\Sigma)$ built from the fusion product of copies of the double $D(G).$ We show that these spaces are invariant under the \emph{quiver homotopy} and that the composition of cobordisms corresponds to a quasi-Hamiltonian reduction. This provides a multiplicative version of the 2D Hamiltonian TQFT of Maiza-Mayrand.