Communications in Number Theory and Physics

Volume 3 (2009)

Number 2

Modular invariants and twisted equivariant K-theory

Pages: 209 – 296



David E. Evans (School of Mathematics, Cardiff University, Cardiff, Wales, United Kingdom)

Terry Gannon (Department of Mathematics, University of Alberta, Canada)


Freed–Hopkins–Teleman expressed the Verlinde algebra as twisted equivariant K-theory. We study how to recover the full system (fusion algebra of defect lines), nimrep (cylindrical partition function), etc. of modular invariant partition functions of conformal field theories associated to loop groups. We work out several examples corresponding to conformal embeddings and orbifolds. We identify a new aspect of the A–D–E pattern of SU(2) modular invariants.

Published 1 January 2009