REPRESENTATIONS OF CUNTZ ALGEBRAS ON FRACTAL SETS

Abstract

We consider representations of Cuntz algebras on self-similar fractal sets for proper/improper systems of contractions. Natural representations, called Hausdorff representations, are associated with self-similar sets and Hausdorff measures in the case of similitudes in Rⁿ. We completely classify the Hausdorff representations up to unitary equivalence. The complete invariant is the list(λ₁^D, . . . ,λ_N^D), where λ_j is the Lipschitz constant of the j th contraction and D is the Hausdorff dimension of the fractal set. Any non-trivial list can be realized by similitudes on the unit interval. There exists an improper system of contractions such that its representation of a Cuntz algebra on the self-similar fractal set is not unitarily equivalent to any Hausdorff representation for a proper system of similitudes in Rⁿ.