On Galois theory from subfactors

We review some concepts of Galois theory for subfactors N⊆MN⊆M, computing some Galois groups and correspondences in this framework. Given an outer action of a group G   on a II1II1 von Neumann factor N and a normal subgroup H of G  , we prove that the fixed point group–subgroup subfactor NG⊆NHNG⊆NH is conjugate to the group–subfactor NG/H⊆NNG/H⊆N.