  The Laplacian (or radial) masa in a free group factor is generated by the sum
of the generators and their inverses. We show that such a masa B is strongly
singular and has Popa invariant delta(B) = 1. This is achieved by proving that
the conditional expectation onto B is an asymptotic homomorphism. We also
obtain similar results for the free product of discrete groups, each of which
contains an element of infinite order.
