Three-Dimensional Spin TFTs from Gauging Line Defects

From the input of an oriented three-dimensional TFT with framed line defects and a commutative $\Delta$-separable Frobenius algebra $A$ in the ribbon category of these line defects, we construct a three-dimensional spin TFT. The framed line defects of the spin TFT are labelled by certain equivariant modules over $A$, and the spin structure may or may not extend to a given line defect. Physically the spin TFT can be interpreted as the result of gauging a one-form symmetry in the original oriented TFT. This spin TFT extends earlier constructions in Blanchet-Masbaum (1996) and Blanchet (2005) [arXiv:math/0303240], and it reproduces the classification of abelian spin Chern-Simons theories in Belov-Moore (2005) [arXiv:hep-th/0505235].