Categorical Continuous Symmetry

Abstract

We define the symmetry category in 1+1d for continuous 0-form $G$-symmetry to be $\textbf{Sky}^\tau(G)$, the category of skyscraper sheaves of finite dimensional vector spaces with finite support on the group manifold of $G$, where $\tau \in H^4(BG,\mathbb{Z})$ is the anomaly. We propose that the corresponding 2+1d SymTFT is described by the Drinfeld center of $\textbf{Sky}^\tau(G)$. We show explicitly the way that $\tau$ twists the convolution tensor product of the objects of $\textbf{Sky}^\tau(G)$. As a concrete example, we present the $S$ and $T$-matrices for the simple anyons of the resulting $Z(\textbf{Sky}^\tau(G))$ category for $G = U(1)$, both for the cases without or with anomaly and discuss the topological boundary conditions as Lagrangian algebra of $Z(\textbf{Sky}^{\tau}(U(1)))$. We also present the definition of $\textbf{Sky}^\tau(G)$ and $Z(\textbf{Sky}^\tau(G))$ for the non-abelian case of $G=SU(2)$, as well as the speculated modular data. We point out that in order to have a physically relevant center and Lagrangian algebras it is necessary to generalize $\textbf{Sky}^\tau(G)$ to a larger category, which we argue to be closely related to the category of quasi-coherent sheaves on $G_\mathbb{C}$ with convolution tensor product twisted by $\tau$.