Fernando J. Sanchez-Salas
Horseshoes with infinitely many branches and a 
characterization of Sinai-Ruelle-Bowen measures
(798K, .ps .dvi)

ABSTRACT.  Let $f$ be a $C^2$ diffeomorphism of a compact riemannian 
manifold $M^m$ and $\mu$ an ergodic f-invariant Borel probability 
with non zero Lyapunov exponents. We prove that $\mu$ is a 
Sinai-Ruelle-Bowen (SRB) measure if and only if we can reduce the 
dynamics on an invariant set of total measure to a horseshoe with 
infinitely many branches and variable return times. Also, and as a 
consequence of our approach we give a new proof of the well known 
Ledrappier-Young's characterization theorem.