O principal objetivo desse trabalho é o estudo da questão da existência de isomorfismos entre as classes de Baire sobre [0,1]. Para isso, desenvolvemos os principais resultados concernentes às relações entre as classes de Baire sobre [0,1]. A saber: (1) As classes de Baire são isométricas como álgebras de Banach a espaços da forma C(K); (2) As classes de Baire são subespaços próprios umas das outras, até o primeiro ordinal não enumerável, onde elas estabilizam; (3) As classes de Baire não são subespaços complementados umas das outras; (4) As classes de Baire não são isométricas umas às outras como espaços de Banach. Por fim, apresentamos as respostas conhecidas para a questão isomórfica, sendo que para tal, utilizamos os resultados mencionados acima. / The main purpose of this work is the study of the question about the existence of isomorphisms between the Baire classes on [0,1]. In order to do that, we develop the most important results concerning the relations between the Baire classes on [0,1]. Those results are: (1) The Baire classes are isometric as Banach algebras to spaces of the form C(K); (2) The Baire classes are proper subspaces each one of the others, until the first uncountable ordinal, when they stabilise; (3) The Baire classes aren\'t complemented subspaces each one of the others; (4) There aren\'t linear isometries between the Baire classes. Finally we presente the known answers to the isomorphic question, using for this the results mentioned above.

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.

This thesis consists of five research papers. The first paper: We prove that under certain conditions, the existence of an isomorphism between spaces of continuous affine functions on the compact convex sets imposes home- omorphism between the sets of its extreme points. The second: We investigate a transfer of descriptive properties of elements of biduals of Banach spaces con- strued as functions on dual unit balls. We also prove results on the relation of Baire classes and intrinsic Baire classes of L1-preduals. The third: We identify intrinsic Baire classes of X with the spaces of odd or homogeneous Baire functions on ext BX∗ , provided X is a separable real or complex L1-predual with the set of extreme points of its dual unit ball of type Fσ. We also provide an example of a separable C∗ -algebra such that the second and second intrinsic Baire class of its bidual differ. The fourth: We generalize some of the above mentioned results for real non-separable L1-preduals. The fifth: We compute the distance of a general mapping to the family of mappings of the first resolvable class via the quantity frag and we introduce and investigate a class of mappings of countable oscillation rank.