Spontaneously broken abelian Chern-Simons theories

TL;DR

This paper analyzes abelian Chern-Simons theories with spontaneously broken gauge groups, revealing how certain topological interactions lead to nonabelian dualities and new types of vortex interactions.

Contribution

It demonstrates how specific 3-cocycles in broken U(1)^k Chern-Simons theories produce nonabelian dualities and novel topological vortex interactions.

Findings

Identification of three types of 3-cocycles for finite abelian groups.

Only certain 3-cocycles are realizable from broken U(1)^k theories.

Duality between specific Chern-Simons theories and nonabelian gauge theories.

Abstract

A detailed analysis of Chern-Simons (CS) theories in which a compact abelian direct product gauge group U(1)^k is spontaneously broken down to a direct product H of (finite) cyclic groups is presented. The spectrum features global H charges, vortices carrying flux labeled by the elements of H and dyonic combinations. Due to the Aharonov-Bohm effect these particles exhibit toplogical interactions. The remnant of the U(1)^k CS term in the discrete H gauge theory describing the effective long distance physics of such a model is shown to be a 3-cocycle for H summarizing the nontrivial topological interactions cast upon the magnetic vortices by the U(1)^k CS term. It is noted that there are in general three types of 3-cocycles for a finite abelian gauge group H: one type describes topological interactions among vortices carrying flux w.r.t. the same cyclic group in the direct product H, another type gives rise to topological interactions between vortices carrying flux w.r.t. two different cyclic factors of H and a third type leading to topological interactions between vortices carrying flux w.r.t. three different cyclic factors. Among other things, it is demonstrated that only the first two types can be obtained from a spontaneously broken U(1)^k CS theory. The 3-cocycles that can not be reached in this way turn out to be the most interesting. They render the theory nonabelian and in general lead to dualities with planar theories with a nonabelian finite gauge group. In particular, the CS theory with finite gauge group H = Z_2 x Z_2 x Z_2 defined by such a 3-cocycle is shown to be dual to the planar discrete D_4 gauge theory with D_4 the dihedral group of order 8.