Metaplectic Categories, Gauging and Property F

Abstract

$N$-Metaplectic categories, unitary modular categories with the same fusion rules as $SO(N{)}_2$, are prototypical examples of weakly integral modular categories. As such, a conjecture of the second author would imply that images of the braid group representations associated with metaplectic categories are finite groups, i.e. have property $F$. While it was recently shown that $SO(N{)}_2$ itself has property $F$, proving property $F$ for the more general class of metaplectic modular categories is an open problem. We verify this conjecture for $N$-metaplectic modular categories when $N$ is odd, exploiting their classification and enumeration to relate them to $SO(N{)}_2$. In another direction, we prove that when $N$ is divisible by $8$ the $N$-metaplectic categories have $3$ non-trivial bosons, and the boson condensation procedure applied to 2 of these bosons yields $\frac{N}{4}$-metaplectic categories. Otherwise stated: any $8k$-metaplectic category is a ${\mathbb{Z}}_2$-gauging of a $2k$-metaplectic category, so that the $N$ even metaplectic categories lie towers of ${\mathbb{Z}}_2$-gaugings commencing with $2k$- or $4k$-metaplectic categories with $k$ odd.

version 3: condensed proofs