  The Turaev-Viro state sum invariant can be extended to 3-manifolds with free
boundaries. We use this fact to describe generalized Frobenius-Schur indicators
as Turaev-Viro invariants of solid tori. This provides a geometric
understanding of the $\mathrm{SL}(2,\mathbb{Z})$-equivariance of these
indicators.

Quantum Algebra