Virtual Classes of Representation Varieties of Upper Triangular Matrices via Topological Quantum Field Theories

arXiv (Cornell University)

Abstract

In this paper, we use a geometric technique developed by González-Prieto, Logares, Muñoz, and Newstead to study the $G$-representation variety of surface groups $\mathfrak{X}_G(Σ_g)$ of arbitrary genus for $G$ being the group of upper triangular matrices of fixed rank. Explicitly, we compute the virtual classes in the Grothendieck ring of varieties of the $G$-representation variety and the moduli space of $G$-representations of surface groups for $G$ being the group of complex upper triangular matrices of rank $2$, $3$, and $4$ via constructing a topological quantum field theory. Furthermore, we show that in the case of upper triangular matrices the character map from the moduli space of $G$-representations to the $G$-character variety is not an isomorphism.

Authors 2

1. Márton Hablicsek Aachen Mathematical Institute

   Leiden University

   Affiliation as printed

   Mathematical Institute , Niels Bohrweg 1 , 2333 CA Leiden , The Netherlands

   Leiden University

2. Jesse Vogel Aachen Mathematical Institute

   Leiden University

   Affiliation as printed

   Mathematical Institute , Niels Bohrweg 1 , 2333 CA Leiden , The Netherlands

   Leiden University