Frobenius algebras associated with the $\alpha$-induction for equivariantly braided tensor categories

Abstract

Let $G$ be a group. We give a categorical definition of the $G$-equivariant $\alpha$-induction associated with a given $G$-equivariant Frobenius algebra in a $G$-braided multitensor category, which generalizes the $\alpha$-induction for $G$-twisted representations of conformal nets. For a given $G$-equivariant Frobenius algebra in a spherical $G$-braided fusion category, we construct a $G$-equivariant Frobenius algebra, which we call a $G$-equivariant $\alpha$-induction Frobenius algebra, in a suitably defined category called neutral double. This construction generalizes Rehren's construction of $\alpha$-induction Q-systems. Finally, we define the notion of the $G$-equivariant full center of a $G$-equivariant Frobenius algebra in a spherical $G$-braided fusion category and show that it indeed coincides with the corresponding $G$-equivariant $\alpha$-induction Frobenius algebra, which generalizes a theorem of Bischoff, Kawahigashi and Longo.