Strongly Singular Masas in Type $II_1$ Factors
arXiv:math/0107075
Abstract
In this paper we introduce and study strongly singular maximal abelian self-adjoint subalgebras of type $II_1$ factors. We show that certain elements of free groups and of non-elementary hyperbolic groups generate such masas, and these also give new examples of masas for which Popa's invariant delta is 1. We also explore the connection between Popa's invariant and strong singularity.
22 pages, latex file, Geom. and Funct. Anal, to appear