Finite index quantum subgroups of discrete quantum groups

Abstract

We show that finite index quantum subgroups of a discrete quantum group are induced from finite index quantum subgroups of the unimodularization. As an application, we classify all finite index quantum subgroups of free products of the duals of connected simply-connected compact Lie groups. We also put proofs for some fundamental facts on finite index right coideals of compact quantum groups.

24 pages