The structure of crossed products of irrational rotation algebras by finite subgroups of SL_2 (Z)

Siegfried Echterhoff, Wolfgang Lueck, N. Christopher Phillips +1

Let F be a finite subgroup of SL_2 (Z) (necessarily isomorphic to one of Z/2Z, Z/3Z, Z/4Z, or Z/6Z), and let F act on the irrational rotational algebra A_θ via the restriction of t…