The topological dynamics of continuous and noncontinuous dynamical systems are investigated. Various definitions of chaos are studied, as well as notions of stability. Results are obtained on asymptotically stable sets and the perturbation stability of such sets. The primary focus is on the traditional point sets of topological dynamics, including the chain recurrent set, omega-limit sets and attractors. The basic setting is that of a continuous function on a compact metric space, sometimes with additional properties on the space. The investigation includes results on the dynamical properties of typical continuous functions in the sense of Baire category. Results are also developed concerning dynamical systems involving quasi-continuous functions. An invariance property for the omega-limit sets of such functions is given. Omega-limit sets are characterized for Riemann integrable derivatives and derivatiyes which are continuous almost everywhere. Techniques used in the investigation and formulation of results include finding theorems which relate the rather disparate notions of dynamical properties and generalized continuity. In addition to dynamical systems, numerous other applications of generalized continuity are imoestigated. Techniques used include application of the Baire Category Theorem and the notion of semi-closure. For example, results are formulated concerning functions determined by dense sets, including separately continuous functions, thus generalizing the classical result for continuous functions on dense subsets of the domain. The uniform boundedness theorem is extended to functions which are not necessarily continuous, including various derivatives. The closed graph theorem is strictly generalized in two separate ways, and applications are presented using these generalizations. An invariance property of separately continuous functions is given. Cluster sets are studied in connection with separate continuity, and various results are presented concerning locally bounded functions.

In this paper, we use the following scheme to construct a continuous, nowhere-differentiable function 𝑓 which is the uniform limit of a sequence of sawtooth functions 𝑓ₙ : [0, 1] → [0, 1] with increasingly sharp teeth. Let 𝑋 = [0, 1] x [0, 1] and 𝐹(𝑋) be the Hausdorff metric space determined by 𝑋. We define contraction maps 𝑤₁ , 𝑤₂ , 𝑤₃ on 𝑋. These maps define a contraction map 𝑤 on 𝐹(𝑋) via 𝑤(𝐴) = 𝑤₁(𝐴) ⋃ 𝑤₂(𝐴) ⋃ 𝑤₃(𝐴). The iteration under 𝑤 of the diagonal in 𝑋 defines a sequence of graphs of continuous functions 𝑓ₙ. Since 𝑤 is a contraction map in the compact metric space 𝐹(𝑋), 𝑤 has a unique fixed point. Hence, these iterations converge to the fixed point-which turns out to be the graph of our continuous, nowhere-differentiable function 𝑓. Chapter 2 contains the background we will need to engage our task. Chapter 3 includes two results from the Baire Category Theorem. The first is the well known fact that the set of continuous, nowhere-differentiable functions on [0,1] is a residual set in 𝐶[0,1]. The second fact is that the set of continuous functions on [0,1] which have a dense set of proper local extrema is residual in 𝐶[0,1]. In the fourth and last chapter we actually construct our function and prove it is continuous, nowhere-differentiable and has a dense set of proper local extrema. Lastly we iterate the set {(0,0), (1,1)} under 𝑤 and plot its points. Any terms not defined in Chapters 2 through 4 may be found in [2,4]. The same applies to the basic properties of metric spaces which have not been explicitly stated. Throughout, we will let 𝒩 and 𝕽 denote the natural numbers and the real numbers, respectively.

Following the classical theory of Baire category results for sets of measure-preserving transformations, this work develops a theory for Baire category results for sets of measure-preserving extensions. First the case is considered where a measure space and a sub-algebra are fixed, and extensions are considered to be any measure-preserving transformations which leave this sub-algebra invariant. In the latter case, extensions of a fixed measure-preserving transformation are considered. In both cases, it is shown that the set of weakly mixing extensions form a dense, G-delta set

L'analyse multifractale est l'étude des propriétés locales des ensembles de mesures ou de fonctions. Son importance est apparue dans le cadre de la turbulence pleinement développée. Dans ce cadre, l'expérimentateur n'a pas accès à la vitesse en tout point d'un fluide mais il peut mesurer sa valeur en un point en fonction du temps. On ne mesure donc pas directement la fonction vitesse du fluide, mais sa trace. Cette thèse sera essentiellement consacrée à l'étude du comportement local de traces de fonctions d'espaces de Besov : nous déterminerons la dimension de Hausdorff des ensembles de points ayant un exposant de Hölder donné (spectre multifractal). Afin de caractériser facilement l'exposant de Hölder et l'appartenance à un espace de Besov, on utilisera la décomposition de fonctions sur les bases d'ondelettes.Nous n'obtiendrons pas la valeur du spectre de la trace de toute fonction d'un espace de Besov mais sa valeur pour un ensemble générique de fonctions. On fera alors appel à deux notions de généricité différentes : la prévalence et la généricité au sens de Baire. Ces notions ne coïncident pas toujours, mais, ici on obtiendra les mêmes résultats. Dans la dernière partie, afin de déterminer la forme que peut prend un spectre multifractal, on construira une fonction qui est son propre spectre

In this thesis we study quantitative weak compactness in spaces (C(K), τp) and later in Banach spaces. In the first chapter we introduce several quantities, which in different manners measure τp-noncompactness of a given uniformly bounded set H ⊂ RK . We apply the results in Banach spaces in chapter 2, where we prove (among others) a quantitative version of the Eberlein-Smulyan theorem. In the third chapter we focus on convex closures and how they affect measures of noncompactness. We prove a quantitative version of the Krein-Smulyan theorem. The first three chapters show that measuring noncompactness is intimately related to measuring distances from function spaces. We follow this idea in chapters 4 and 5, where we measure distances from Baire one functions first in RK and later also in Banach spaces. 1

L'objet de cette thèse est l'étude de la complexité topologique de fonctions omega-rationnelles : fonctions de mots infinis dont le graphe est reconnaissable par automate fini. Le cadre de notre étude est celui de la hiérarchie des boréliens et des classes de Baire. On remarque tout d'abord que ces fonctions sont au plus de classe 2. Christophe Prieur a montré que le problème de la continuité est décidable. Nous avons montré qu'être de classe 1 est aussi décidable dans le cas synchrone en adaptant un résultat de Sierpinski portant sur les sur et sous-graphes à notre contexte. Notre attention s'est ensuite portée aux points de continuité de telles fonctions. Un résultat de Baire dit qu'une fonction n'est pas de classe 1 si et seulement si il existe un fermé non vide sur lequel la fonction n'admet aucun point de continuité. Nous prouvons une version automate de ce théorème : Une fonction omega-rationnelle n'est pas de classe 1 si et seulement si il existe un fermé non vide reconnaissable par un automate de Büchi tel que la restriction de la fonction à ce fermé n'ait aucun point de continuité. Ce résultat est prouvé en utilisant la dérivation de Hausdorff qui s'arrête au bout d'un nombre fini d'étapes sur les langages omega-rationnels Ce travail s'est conclu par l'étude des orbites des fonctions réelles définissables en base Pisot par des transducteurs synchrones. L'ordre de Sarkovski permet de classifier les ordres des orbites périodiques des fonction réelles continues. Le résultat principal obtenu est la décidabilité pour tout entier n de l'existence d'orbites périodiques de cardinalité n et par suite de toute cardinalité inférieure dans l'ordre de Sarkovski.

In our dissertation we deal with the space H(K) of harmonic functions on a compact space in classical and abstract potential theory. Initially, we prove several equivalent characteristics of this space in classical potential theory. The internal characterization, which describes H(K) as a subspace of those continuous functions on a compact space K which are finely harmonic on the fine interior of K, is then used as the definition of H(K) in abstract potential theory. Further we concentrate on the solution of the Dirichlet problem for open and compact sets mainly with regards to its relation to subclasses of Baire class one functions. The results, proved at first in classical potential theory, are later generalized to abstract potential theory. With a use of more elemen- tary tools we initially prove these results in harmonic spaces with the axiom of dominance and, subsequently, using stronger tools we generalize them to harmonic spaces with the axiom of polarity. We engage also in a more abstract problem of approximation by differen- ces of lower semicontinuous functions in a more general context of binormal topological spaces.

Title: Baire and Harmonic Functions Author: Petr Pošta Department: Department of Mathematical Analysis Supervisor: prof. RNDr. Jaroslav Lukeš, DrSc., Department of Mathematical Analysis Abstract: The present thesis consists of six research papers. The first four articles deal with topics related to potential theory, Baire-one functions and its important subclasses, in particular differences of semicontinuous functions. The first paper is devoted to the stability of the Dirichlet problem for which a new criterion in terms of Poisson equation is provided. The second paper improves the recent result obtained by Lukeš et al. It shows that the classical Dirichlet solution belongs to the B1/2 subclass of Baire-one functions. A generalization of this result to the abstract context of the Choquet theory on functions spaces is provided. Finally, an abstract Dirichlet problem for the boundary condition belonging to the class of differences of semincontinuous functions is discussed. The third paper concentrates on the Lusin-Menshov property and the approximation of Baire- one and finely continuous functions by differences of semicontinuous and finely continuous functions. It provides an exposition of topologies (various density topologies as well as the fine topologies in both linear and non-linear potential...