2 5 N ov 2 00 3 HYPERBOLIC TIMES : FREQUENCY VS . INTEGRABILITY

We consider dynamical systems on compact manifolds, which are local dif-feomorphisms outside an exceptional set (a compact submanifold). We are interested in analyzing the relation between the integrability (with respect to Lebesgue measure) of the first hyperbolic time map and the existence of positive frequency of hyperbolic times. We show that some (strong) integrability of the first hyperbolic time map implies positive frequency of hyperbolic times. We also present an example of a map with positive frequency of hyperbolic times at Lebesgue almost every point but whose first hyperbolic time map is not integrable with respect to the Lebesgue measure.