We prove a perturbation lemma for the derivative of geodesic flows in high dimension. This implies that a C generic riemannian metric has a non-trivial hyperbolic basic set in its geodesic flow.

We investigate an analogue of the L 2-Betti numbers for amenable linear sub-shifts. The role of the von Neumann dimension shall be played by the topological entropy.

Let (X, d) be a compact metric space, f : X 7→ X be a continuous map satisfying a property we call almost specification (which is slightly weaker than the g-almost product property of Pfister and Sullivan), and φ : X 7→ R be a continuous function. We show that the set of points for which the Birkhoff average of φ does not exist (which we call the irregular set) is either empty or has full topol...

We introduce notions of dimension and dynamical entropy for unital Calgebras “metrized” by means of cLip-norms, which are complex-scalar versions of the Lip-norms constitutive of Rieffel’s compact quantum metric spaces. Our examples involve the UHF algebras Mp∞ and noncommutative tori. In particular we show that the entropy of a noncommutative toral automorphism with respect to the canonical cL...

We extend the definition of algebraic entropy to endomorphisms of affine varieties. We calculate algebraic entropy of the action of elements of mapping class groups on various character varieties, and show that it is equal to a quantity we call the spectral radius, a generalization of the dilatation of a Pseudo-Anosov mapping class. Our calculations are compatible with all known calculations of...

Let C r ((0; 1]) denote the metric space of C r self-maps of 0; 1] and C s;r ((0; 1]) denote the metric space of C s families of maps in C r ((0; 1]) with the parameter space 0; 1]. Let Hs;r be the unimodal families with non-constant topological entropy in C s;r ((0; 1]). We show that for s 0, r 2, there is an open and dense subset Gs;r of Hs;r such that each family in Gs;r has a map with a hom...

We establish the analogue for maps on trees of the result established in [Bob02, Bob05] for interval maps, that a continuous selfmap for which all but countably many points have at least m preimages (and none have less than two) has topological entropy bounded below by logm.

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 homology. Moreover, they admit principal symbolic extensions, and the topological entropy and metrical entropy vary continuously wit...

Let X be a compact metric space and let f : X → X be continuous. It is well known that a given discrete dynamical system (X, f) induces a map Φ on the space F(X) of fuzzy sets. In this paper we study relations between sizes of topological entropies of a given crisp dynamical system (X, f) and its fuzzy counterpart (F(X),Φ). Among another things, we present a constructive proof of the fact that ...

In the first part of these notes we survey results on entropy for smooth systems. We emphasize questions regarding existence and uniqueness of measures of maximal entropy, changes of topological entropy under perturbations, and entropy structures for smooth systems. In the second part of these notes we review topological pressure and equilibrium states for smooth systems. We look at existence a...