The Flow of Weights in Subfactor Theory

Abstract

We define a Connes-Takesaki type flow of weights for any inclusion of factors. It is shown that Popa's classification of strongly amenable subfactors as well as some new structural results on type III-subfactors can be stated in a unified way using this invariant. The invariant also separates certain "exotic" examples of subfactors which are not covered by that classification.