A classification of all finite index subfactors for a class of group-measure space II_1 factors
arXiv:1002.2129
Abstract
We provide a family of group measure space II_1 factors for which all finite index subfactors can be explicitly listed. In particular, the set of all indices of irreducible subfactors can be computed. Concrete examples show that this index set can be any set of natural numbers that is closed under taking divisors.
Minor modifications, final version