On the kernel of $\mathrm{SO}(3)$-Witten-Reshetikhin-Turaev quantum representations

Abstract

In this paper, we study the kernels of the $\mathrm{SO}(3)$-Witten-Reshetikhin-Turaev quantum representations ${\rho }_p$ of mapping class groups of closed orientable surfaces ${\Sigma }_g$ of genus $g.$ We investigate the question whether the kernel of ${\rho }_p$ for $p$ prime is exactly the subgroup generated by $p$-th powers of Dehn twists. We show that if $g\ge 3$ and $p\ge 5$ then $\mathrm{Ker}{\rho }_p$ is contained in the subgroup generated by $p$-th powers of Dehn twists and separating twists, and if $g\ge 6$ and $p$ is a large enough prime then $\mathrm{Ker}{\rho }_p$ is contained in the subgroup generated by the commutator subgroup of the Johnson subgroup and by $p$-th powers of Dehn twists.

25 pages, 9 figures. Typo corrected