Multifractal formalism for Benedicks-Carleson quadratic maps

Abstract: For a positive measure set of nonuniformly expanding quadratic maps on the interval we effect a multifractal formalism, i.e., decompose the phase space into level sets of time averages of a given observable and consider the associated {\it Birkhoff spectrum} which encodes this decomposition. We derive a formula which relates the Hausdorff dimension of level sets to entropies and Lyapunov exponents of invariant probability measures, and then use this formula to show that the spectrum is continuous. In order to estimate the Hausdorff dimension from above, one has to "see" sufficiently many points. To this end, we construct a family of towers. Using these towers we establish a large deviation principle for empirical distributions, with Lebesgue as a reference measure.