Interpolated free group factors

Abstract

The interpolated free group factors L(F_r), 1 < r <= \infty, are defined and proofs of their properties with respect to compression by projections and taking free products are proved. Hence it follows that all the free group factor are isomorphic to each other or none of them are. These factors were defined and these properties were proved independently by F. Radulescu, and those given in this paper are equivalent, but use different techniques. Specifically, we develop algebraic techniques that allow us to show that R*R = L(F_2), where R is the hyperfinite II_1 factor.