Nonuniform measure rigidity

We consider an ergodic invariant measure μ for a smooth action α of Z^k, k ≥ 2, on a (k + 1)-dimensional manifold or for a locally free smooth action of R^k, k ≥ 2, on a (2k+1)-dimensional manifold. We prove that if μ is hyperbolic with the Lyapunov hyperplanes in general position and if one element in Z^k has positive entropy, then μ is absolutely continuous. The main ingredient is absolute continuity of conditional measures on Lyapunov foliations which holds for a more general class of smooth actions of higher rank abelian groups.