Skein module dimensions of mapping tori of the 2-torus

Abstract

We determine the dimension of the Kauffman bracket skein module at generic $q$ for mapping tori of the 2-torus, generalising the well-known computation of Carrega and Gilmer. In the process, we give a decomposition of the twisted Hochschild homology of the $G$-skein algebra for $G = \mathrm{SL}_N$ or $\mathrm{GL}_N$, which is a direct summand of the whole skein module, and from which the dimensions follow easily in the cases $G = \mathrm{SL}_2$ and $G = \mathrm{GL}_1$.