On homeomorphic product measures on the Cantor set

Abstract

Let mu(r) be the Bernoulli measure on the Cantor space given as the infinite product of two-point measures with weights r and 1-r. It is a long-standing open problem to characterize those r and s such that mu(r) and mu(s) are topologically equivalent (i.e., there is a homeomorphism from the Cantor space to itself sending mu(r) to mu(s)). The (possibly) weaker property of mu(r) and mu(s) being continuously reducible to each other is equivalent to a property of r and s called binomial equivalence. In this paper we define an algebraic property called "refinability" and show that, if r and s are refinable and binomially equivalent, then mu(r) and mu(s) are topologically equivalent. We then give a class of examples of refinable numbers; in particular, the positive numbers r and s such that s=r^2 and r=1-s^2 are refinable, so the corresponding measures are topologically equivalent.