The entropy conjecture for diffeomorphisms away from tangencies

Abstract

We prove that every C1 diffeomorphism away from homoclinic tangencies is entropy expansive, with locally uniform expansivity constant. Consequently, such diffeomorphisms satisfy Shub's entropy conjecture: the entropy is bounded from below by the spectral radius in homo-logy. Moreover, they admit principal symbolic extensions, and the topological entropy and metrical entropy vary upper semicontinuously with the map. In contrast, generic diffeomorphisms with persistent tangencies are not entropy expansive. © European Mathematical Society 2013.