On Galois theory from subfactors

We review some concepts of Galois theory for subfactors N#M, computing some Galois groups and correspondences in this framework. Given an outer action of a group G on a II1 von Neumann factor N and a normal subgroup H of G, we prove that the fixed point group–subgroup subfactor NG #NH is conjugate to the group–subfactor NG=H #N.