paper

Non-Abelian String and Particle Braiding in Topological Order: Modular SL(3,Z) Representation and 3+1D Twisted Gauge Theory

arXiv:1404.7854 · doi:10.1103/PhysRevB.91.035134

Abstract

String and particle braiding statistics are examined in a class of topological orders described by discrete gauge theories with a gauge group and a 4-cocycle twist of 's cohomology group in 3 dimensional space and 1 dimensional time (3+1D). We establish the topological spin and the spin-statistics relation for the closed strings, and their multi-string braiding statistics. The 3+1D twisted gauge theory can be characterized by a representation of a modular transformation group SL. We express the SL generators and in terms of the gauge group and the 4-cocycle . As we compactify one of the spatial directions into a compact circle with a gauge flux inserted, we can use the generators and of an SL subgroup to study the dimensional reduction of the 3D topological order to a direct sum of degenerate states of 2D topological orders in different flux sectors: . The 2D topological orders are described by 2D gauge theories of the group twisted by the 3-cocycles , dimensionally reduced from the 4-cocycle . We show that the SL generators, and , fully encode a particular type of three-string braiding statistics with a pattern that is the connected sum of two Hopf links. With certain 4-cocycle twists, we discover that, by threading a third string through two-string unlink into three-string Hopf-link configuration, Abelian two-string braiding statistics is promoted to non-Abelian three-string braiding statistics.

36 pages, many figures, 17 tables. v3: Accepted by Phys. Rev. B. Add acknowledgements to Louis H. Kauffman

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