M.Sc.

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A fixed point of a mapping is an element in the domain of the mapping that is mapped into itself by the mapping. The study of fixed points has been a field of interests to mathematicians since the discovery of the Banach contraction theorem, i.e. if is a complete metric space and is a contraction mapping (i.e. there exists such that for all ), then has a unique fixed point. The Banach contraction theorem has found many applications in pure and applied mathematics. Due to fixed point theory being a mixture of analysis, geometry, algebra and topology, its applications to other fields such as physics, economics, game theory, chemistry, engineering and many others has become vital. The theory is nowadays a very active field of research in which many new theorems are published, some of them applied and many others generalized. Motivated by all of this, we give an exposition of some generalizations of fixed point theorems in metric fixed point theory, which is a branch of fixed point theory about results of fixed points of mappings between metric spaces, where certain properties of the mappings involved need not be preserved under equivalent metrics. For instance, the contractive property of mappings between metric spaces need not be preserved under equivalent metrics. Since metric fixed point theory is wide, we limit ourselves to fixed point theorems for self and non-self-mappings on Banach and metric spaces. We also take a look at some open problems on this topic of study. At the end of the dissertation, we suggest our own problems for future research.

A norm ||⋅|| on a Banach space X is Fréchet differentiable at x ∈ X if there is a functional ∫∈ X* such that [Formula Omitted] This concept reflects the smoothness characteristics of X. A dual Banach space X* has the Radon-Nikodym Property (RNP) if whenever C ⊂ X* is weak*-compact and convex, and ∈ > 0, there is an x ∈ X and an ⍺ > 0 such that diameter [Formula Omitted] this property reflects the convexity characteristics of X*. Culminating several years of work by many researchers, the following theorem established a strong connection between the smoothness of X and the convexity of X*: Every equivalent norm on X is Fréchet differentiable on a dense set if and only if X* has the RNP. A more general measure of convexity has been recently receiving a great deal of attention: A dual Banach space X* has the weak* Convex Point-of-Continuity Property (C*PCP) if whenever ɸ ≠ C ⊂ X* is weak*-compact and convex, and ∈ > 0, there is a weak*-open set V such that V ⋂ C ≠ ɸ and diam V ⋂ C < ∈. In this thesis, we develop the corresponding smoothness properties of X which are dual to C*PCP. For this, a new type of differentiability, called cofinite Fréchet differentiability, is introduced, and we establish the following theorem: Every equivalent norm on X is cofinitely Fréchet differentiable everywhere if and only if X* has the C*PCP. Representing joint work with R. Deville, G. Godefroy and V. Zizler, an alternate approach is developed in the case when X is separable. We show that if X is separable, then every equivalent norm on X which has a strictly convex dual is Fréchet differentiable on a dense set if and only if X* has the C*PCP, if and only if every equivalent norm on X which is Gâteaux differentiable (everywhere) is Fréchet differentiable on a dense set. This result is used to show that if X* does not have the C*PCP, then there is a subspace Y of X such that neither Y* nor (X/Y)* have the C*PCP, yet both Y and X/Y have finite dimensional Schauder decompositions. The corresponding result for spaces X* failing the RNP remains open. / Science, Faculty of / Mathematics, Department of / Graduate

We study the relationship between real and complex tensor norms. The theory of tensor norms on tensor products of Banach spaces, was developed, by A. Grothendieck, in his Resumé de la théorie métrique des produits tensoriels topologiques [3]. In this monograph he introduced a variety of ways to assign norms to tensor products of Banach spaces. As is usual in functional analysis, the real-scalar theory is very closely related to the complex-scalar theory. For example, there are, up to top ological equivalence, fourteen ``natural' tensor norms in each of the real-scalar and complex-scalar theories. This correspondence was remarked upon in the Resumé, but without proving any formal relationships, although hinting at a certain injective relationship between real and complex (topological) equivalence classes of tensor norms. We make explicit connections between real and complex tensor norms in two different ways. This divides the dissertation into two parts. In the first part, we consider the ``complexifications' of real Banach spaces and find tensor norms and complexification procedures, so that the complexification of the tensor product, which is itself a Banach space, is isometrically isomorphic to the tensor product of the complexifications. We have results for the injective tensor norm as well as the projective tensor norm. In the second part we look for isomorphic results rather than isometric. We show that one can define the complexification of real tensor norm in a natural way. The main result is that the complexification of real topological equivalence classes that is induced by this definition, leads to an injective correspondence between the real and the complex tensor norm equivalence classes. / Thesis (PHD)--University of Pretoria, 2009. / Mathematics and Applied Mathematics / unrestricted

Orientador: Jorge Tulio Mujica Ascui / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica / Made available in DSpace on 2018-07-31T18:00:37Z (GMT). No. of bitstreams: 1 CarrionVillarroel_HumbertoDaniel_D.pdf: 729207 bytes, checksum: 8a0cb61e3e4019f6e3dfe8cae9e8d014 (MD5) Previous issue date: 2002 / Resumo: Sejam E e F espaços de Banach complexos. Denotamos por H(E; F) o espaço das funções holomorfas de E em F. Denotamos também por HW(E; F) (resp. HWU(E; F) o subespaço de H(E: F) constituído pelas funções holomorfas que são fracamente contínuas ( resp. fracamente uniformemente contínuas ) nos limitados de E. Em 1983 Aron, Hervés e Valdivia levantam a seguinte questão: HW(E; F)=HWU(E\ F), para quaisquer espaços de Banach E e F? Seja HWSC(E\ F) o espaço das funções inteiras que levam seqüências fracamente convergentes em seqüências convergentes era norma. Relacionado ao problema anterior Aron, Hervés e Valdivia propuseram também: Hwsc(E\ F)= HWU(E; F), se E tem dual separável é F é arbitrário? Denotando por HBK (E;F) o espaço das funções holomorfas limitadas nos subconjuntos fracamente compactos, e modificando as técnicas de Dineen [4] mostramos que se E tem dual separável então a relação Hb(E;F)=Hbk (E;F) é satisfeita. Isto responde parcialmente em forma afirmativa à primeira questão e completamente à segunda / Abstract: Let E and F be complex Banach spaces, and let H (E; F) be the space of all holomorphic functions from E into F. We also denote by HW (E; F) (resp. HWU (E; F)) the subspace of all ¿ ? H (E; F) which are weakly continuous on bounded sets (resp. weakly uniformly continuous on bounded sets).In 1983 Aron, Herves and Valdivia raised the following question: Does Hw {E; F) = HWU (E; F) for arbitrary E and F? Let HWSC (E; F) be the subspace of all ¿ ? H (E; F) which map weakly convergent sequences onto norm convergent sequences. Related to the preceding problems Aron, Herves and Valdivia raised also.Does Hwsd (E;F) = HWU (E\ F) when E has separable dual and F is arbitrary Denoting by Hbk (E;F) (resp. Hb (E:F)) the subspace of all ¿ ? H (E; F) which are bounded on weakly compact sets (resp. bounded on bounded set) and modifying the techniques of Dineen [4] we show that if E has a separable dual then the relation Hbk(E:F)=Hb(E;F) is satisfied. This answers partially the first question and completely the second question / Doutorado / Doutor em Matemática

Orientador : João Bosco Prolla / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Científica / Made available in DSpace on 2018-07-17T12:18:00Z (GMT). No. of bitstreams: 1 Roversi_MariaSueliMarconi_D.pdf: 1345632 bytes, checksum: fa42a6c421942562540b8768b76022ae (MD5) Previous issue date: 1982 / Resumo: Não informado / Abstract: Not informed / Doutorado / Doutor em Matemática

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