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Sei V ein holomorphes Vektorbündel über einer q-konvexen Mannigfaltigkeit X. Die Andreotti-Grauert-Theorie sagt, dass die r-te Kohomologiegruppe holomorpher Schnitte mit Werten in V endlich-dimensional ist und dass die Kohomologie verschwindet, falls X q-vollständig ist. Ist E ein holomorphes Banachbündel über X, dann ist bekannt, dass die erste Kohomologiegruppe verschwindet, falls X Steinsch ist. Kapitel I gibt einen ausführlichen Überblick über die Arbeit. In Kapitel II wird gezeigt, dass es holomorphe Hilbertbündel über 1-konvexen Mannigfaltigkeiten gibt, für die die erste Kohomologie nicht Hausdorffsch ist. In Kapitel III wird folgender Endlichkeitssatz gezeigt: Ist E ein holomorph triviales Banachbündel oder ein holomorphes Banachbündel von kompaktem Typ mit kompakter Approximationseigenschaft über einer q-konvexen Mannigfaltigkeit X, und ist V ein holomorphes Vektorbündel über X, für das die q-te Kohomologie verschwindet, dann gilt: Die q-te Kohomologie für das Tensorprodukt von V und E ist endlich-dimensional. Ist X q-vollständig, dann verschwindet die r-te Kohomologie, falls r größer oder gleich q ist. Für r größer q kann dies auch für beliebige holomorphe Banachbündel E gezeigt werden. Im Anhang wird skizziert, wie der Ansatz der L2-Methode im Fall r gleich q für Hilbertbündel zu einem Verschwindungssatz führen könnte. / Let V be a holomorphic vector bundle over a q-convex manifold X. The Andreotti-Grauert theory says that the r-th cohomology group of holomorphic section with values in V is finite dimensional and that the cohomology is vanishing if X is q-complete. If E is a holomorphic Banach bundle over X, it is known that the first cohomology group vanishes if X is Stein. Chapter I gives a detailed overview of the work. In chapter II it is shown that there are holomorphic Hilbert bundles over 1-convex manifolds such that the first cohomology of the bundle is not Hausdorff. In chapter III the following finiteness theorem is shown: If E is a holomorphically trivial Banach bundle or a holomorphic Banach bundle of compact type with the compact approximation property over a q-convex manifold X, and if V is a holomorphic vector bundle over X such that the q-th cohomology vanishes, then the following holds true: The q-th cohomology for the tensor product of V and E is finite dimensional. If X is q-complete, then the r-th cohomology vanishes if r is greater or equal q. If r is greater than q, this is shown also for arbitrary holomorphic Banach bundles E. In the appendix it is sketched how for r equal q the L2 method could yield a vanishing theorem for Hilbert bundles.

A classificação isomorfa dos espaços de Banach separáveis C(K) é devida a Milutin no caso em que K são não enumeráveis e a Bessaga e Pelczynski no caso em que K são enumeráveis. Neste trabalho apresentamos uma extensão vetorial dessa classificação e tiramos várias consequências, por exemplo, considerando o espaço métrico compacto infinito K e Y um espaço de Banach: &nbsp; &nbsp; 1. Sendo 1 < p < &infin; e &Gamma; um conjunto infinito, classificamos, a menos de isomorfismo, os espaços de Banach C(K, Y &oplus; lp(&Gamma;)), quando o dual de Y contém uma cópia de lq, onde 1/p+ 1/q =1. &nbsp; &nbsp; 2. Classificamos os espaços de Banach C(K, Y &oplus; l&infin;(&Gamma;)), quando a densidade de Y é estritamente menor que 2|&Gamma;|. &nbsp; &nbsp; 3. Classificamos os espaços de Banach C(K &times;(S&oplus; &beta;&Gamma;)) e C(S &oplus; (K&times; &beta;&Gamma;)), onde S é um compacto disperso de Hausdorff arbitrário e &beta;&Gamma; é a compactificação de Stone-Cech de &Gamma;. Obtemos, também, algumas leis de cancelamento para espaços de Banach da forma C(K1,X)&oplus; C(K2,Y), onde K1 e K2 são espaços compactos métricos infinitos de Hausdorff e X, Y espaços de Banach satisfazendo condições adequadas. Estabelecemos também um teorema de quase-dicotomia envolvendo os espaços C(K,X), onde X tem cotipo finito. Finalmente, apresentamos algumas majorações nas distorções de isomorfismos positivos de C([0,&omega;k]) em C([0,&omega;]) e também de C([0,&omega;]) em C([0,&omega;k]), k&isin; N, k &ge; 2. / The isomorphic classification of separable Banach spaces C(K) is due Milutin in the case when K are uncountable and to Bessaga and Pelczynski in the case when K are countable. In this work we prove a vectorial extention of this classification and provide several consequences, for example considering the infinite metric compact space K and Y a Banach space: &nbsp; &nbsp; 1. Let 1 < p < &infin; and &Gamma; a infinite set, we classify, up to an isomorphism, the Banach spaces C(K, Y &oplus; lp(&Gamma;)), in the case where the dual of Y contains no copy of lq, where 1/p+ 1/q =1. &nbsp; &nbsp; 2. We classify the Banach spaces C(K, Y &oplus; l&infin;(&Gamma;)), when the density character of Y is strictly less that 2|&Gamma;|. &nbsp; &nbsp; 3. We classify the Banach spaces C(K &times;(S&oplus; &beta;&Gamma;)) and C(S &oplus; (K&times; &beta;&Gamma;)) where S is an arbitrary dispersed compact and &beta;&Gamma; is the Stone-Cech compactification of &Gamma;. We obtain also some cancellation laws for Banach spaces in the form C(K1,X)&oplus; C(K2,Y), where K1 and K2 are metric compact Hausdorff spaces and X, Y Banach spaces satisfying appropriate conditions. We established also a quasi-dichotomy theorem envolving the C(K,X) spaces, where X is of finite cotype. Finally, we present some upper bounds of distortions of positive isomorphisms of C([0,&omega;k]) on C([0,&omega;]) and also of C([0,&omega;]) on C([0,&omega;k]), k&isin; N, k &ge; 2.

Recall that a Banach space X has the Dunford-Pettis property if every weakly compact operator defined on X takes weakly compact sets into norm compact sets. Some valuable characterisations of Banach spaces with the Dunford-Pettis property are: X has the DPP if and only if for all Banach spaces Y, every weakly compact operator from X to Y sends weakly convergent sequences onto norm convergent sequences (i.e. it requires that weakly compact operators on X are completely continuous) and this is equivalent to “if (xn) and (x*n) are sequences in X and X* respectively and limn xn = 0 weakly and limn x*n = 0 weakly then limn x*n xn = 0". A striking application of the Dunford-Pettis property (as was observed by Grothendieck) is to prove that if X is a linear subspace of L() for some finite measure  and X is closed in some Lp() for 1 ≤ p < , then X is finite dimensional. The fact that the well known spaces L1() and C() have this property (as was proved by Dunford and Pettis) was a remarkable achievement in the early history of Banach spaces and was motivated by the study of integral equations and the hope to develop an understanding of linear operators on Lp() for p ≥ 1. In fact, it played an important role in proving that for each weakly compact operator T : L1()  L1() or T : C()  C(), the operator T2 is compact, a fact which is important from the point of view that there is a nice spectral theory for compact operators and operators whose squares are compact. There is an extensive literature involving the Dunford-Pettis property. Almost all the articles and books in our list of references contain some information about this property, but there are plenty more that could have been listed. The reader is for instance referred to [4], [5], [7], [8], [10], [17] and [24] for information on the role of the DPP in different areas of Banach space theory. In this dissertation, however, we are motivated by the two papers [7] and [8] to study alternative Dunford-Pettis properties, to introduce a scale of (new) alternative Dunford-Pettis properties, which we call DP*-properties of order p (briefly denoted by DP*P), and to consider characterisations of Banach spaces with these properties as well as applications thereof to polynomials and holomorphic functions on Banach spaces. In the paper [8] the class Cp(X, Y) of p-convergent operators from a Banach space X to a Banach space Y is introduced. Replacing the requirement that weakly compact operators on X should be completely continuous in the case of the DPP for X (as is mentioned above) by “weakly compact operators on X should be p-convergent", an alternative Dunford-Pettis property (called the Dunford-Pettis property of order p) is introduced. More precisely, if 1 ≤ p ≤ , a Banach space X is said to have DPPp if the inclusion W(X, Y)  Cp(X, Y) holds for all Banach spaces Y . Here W(X, Y) denotes the family of all weakly compact operators from X to Y. We now have a scale of “Dunford-Pettis like properties" in the sense that all Banach spaces have the DPP1, if p < q, then each Banach space with the DPPq also has the DPPp and the strongest property, namely the DPP1 coincides with the DPP. In the paper [7] the authors study a property on Banach spaces (called the DP*-property, or briey the DP*P) which is stronger than the DPP, in the sense that if a Banach space has this property then it also has DPP. We say X has the DP*P, when all weakly compact sets in X are limited, i.e. each sequence (x*n)  X * in the dual space of X which converges weak* to 0, also converges uniformly (to 0) on all weakly compact sets in X. It turns out that this property is equivalent to another property on Banach spaces which is introduced in [17] (and which is called the *-Dunford-Pettis property) as follows: We say a Banach space X has the *-Dunford-Pettis property if for all weakly null sequences (xn) in X and all weak* null sequences (x*n) in X*, we have x*n(xn) n 0. After a thorough study of the DP*P, including characterisations and examples of Banach spaces with the DP*P, the authors in [7] consider some applications to polynomials and analytic functions on Banach spaces. Following an extensive literature study and in depth research into the techniques of proof relevant to this research field, we are able to present a thorough discussion of the results in [7] and [8] as well as some selected (relevant) results from other papers (for instance, [2] and [17]). This we do in Chapter 2 of the dissertation. The starting point (in Section 2.1 of Chapter 2) is the introduction of the so called p-convergent operators, being those bounded linear operators T : X  Y which transform weakly p-summable sequences into norm-null sequences, as well as the so called weakly p-convergent sequences in Banach spaces, being those sequences (xn) in a Banach space X for which there exists an x  X such that the sequence (xn - x) is weakly p-summable. Using these concepts, we state and prove an important characterisation (from the paper [8]) of Banach spaces with DPPp. In Section 2.2 (of Chapter 2) we continue to report on the results of the paper [7], where the DP*P on Banach spaces is introduced. We focus on the characterisation of Banach spaces with DP*P, obtaining among others that a Banach space X has DP*P if and only if for all weakly null sequences (xn) in X and all weak* null sequences (x*n) in X*, we have x*n(xn) n 0. An important characterisation of the DP*P considered in this section is the fact that X has DP*P if and only if every T  L(X, c0) is completely continuous. This result proves to be of fundamental importance in the study of the DP*P and its application to results on polynomials and holomorphic functions on Banach spaces. To be able to report on the applications of the DP*P in the context of homogeneous polynomials and analytic functions on Banach spaces, we embark on a study of “Complex Analysis in Banach spaces" (mostly with the focus on homogeneous polynomials and analytic functions on Banach spaces). This we do in Chapter 3; the content of the chapter is mostly based on work in the books [23] and [14], but also on the work in some articles such as [15]. After we have discussed the relevant theory of complex analysis in Banach spaces in Chapter 3, we devote Chapter 4 to considering properties of polynomials and analytic functions on Banach spaces with DP*P. The discussion in Chapter 4 is based on the applications of DP*P in the paper [7]. Finally, in Chapter 5 of the dissertation, we contribute to the study of “Dunford-Pettis like properties" by introducing the Banach space property “DP*P of order p", or briefly the DP*Pp for Banach spaces. Using the concept “weakly p-convergent sequence in Banach spaces" as is defined in [8], we define weakly-p-compact sets in Banach spaces. Then a Banach space X is said to have the DP*-property of order p (for 1 ≤ p ≤ ) if all weakly-p-compact sets in X are limited. In short, we say X has DP*Pp. As in [8] (where the DPPp is introduced), we now have a scale of DP*P-like properties, in the sense that all Banach spaces have DP*P1 and if p < q and X has DP*Pq then it has DP*Pp. The strongest property DP*P coincides with DP*P. We prove characterisations of Banach spaces with DP*Pp, discuss some examples and then consider applications to polynomials and analytic functions on Banach spaces. Our results and techniques in this chapter depend very much on the results obtained in the previous three chapters, but now we have to find our own correct definitions and formulations of results within this new context. We do this with some success in Sections 5.1 and 5.2 of Chapter 5. Chapter 1 of this dissertation provides a wide range of concepts and results in Banach spaces and the theory of vector sequence spaces (some of them very deep results from books listed in the bibliography). These results are mostly well known, but they are scattered in the literature - they are discussed in Chapter 1 (some with proof, others without proof, depending on the importance of the arguments in the proofs for later use and depending on the detail with which the results are discussed elsewhere in the literature) with the intention to provide an exposition which is mostly self contained and which will be comfortably accessible for graduate students. The dissertation reflects the outcome of our investigation in which we set ourselves the following goals: 1. Obtain a thorough understanding of the Dunford-Pettis property and some related (both weaker and stronger) properties that have been studied in the literature. 2. Focusing on the work in the paper [8], understand the role played in the study of difierent classes of operators by a scale of properties on Banach spaces, called the DPPp, which are weaker than the DP-property and which are introduced in [8] by using the weakly p-summable sequences in X and weakly null sequences in X*. 3. Focusing on the work in the paper [7], investigate the DP*P for Banach spaces, which is the exact property to answer a question of Pelczynsky's regarding when every symmetric bilinear separately compact map X x X  c0 is completely continuous. 4. Based on the ideas intertwined in the work of the paper [8] in the study of a scale of DP-properties and the work in the paper [7], introduce the DP*Pp on Banach spaces and investigate their applications to spaces of operators and in the theory of polynomials and analytic mappings on Banach spaces. Thereby, not only extending the results in [7] to a larger family of Banach spaces, but also to find an answer to the question: “When will every symmetric bilinear separately compact map X x X  c0 be p-convergent?" / Thesis (M.Sc. (Mathematics))--North-West University, Potchefstroom Campus, 2012.

Recall that a Banach space X has the Dunford-Pettis property if every weakly compact operator defined on X takes weakly compact sets into norm compact sets. Some valuable characterisations of Banach spaces with the Dunford-Pettis property are: X has the DPP if and only if for all Banach spaces Y, every weakly compact operator from X to Y sends weakly convergent sequences onto norm convergent sequences (i.e. it requires that weakly compact operators on X are completely continuous) and this is equivalent to “if (xn) and (x*n) are sequences in X and X* respectively and limn xn = 0 weakly and limn x*n = 0 weakly then limn x*n xn = 0". A striking application of the Dunford-Pettis property (as was observed by Grothendieck) is to prove that if X is a linear subspace of L() for some finite measure  and X is closed in some Lp() for 1 ≤ p < , then X is finite dimensional. The fact that the well known spaces L1() and C() have this property (as was proved by Dunford and Pettis) was a remarkable achievement in the early history of Banach spaces and was motivated by the study of integral equations and the hope to develop an understanding of linear operators on Lp() for p ≥ 1. In fact, it played an important role in proving that for each weakly compact operator T : L1()  L1() or T : C()  C(), the operator T2 is compact, a fact which is important from the point of view that there is a nice spectral theory for compact operators and operators whose squares are compact. There is an extensive literature involving the Dunford-Pettis property. Almost all the articles and books in our list of references contain some information about this property, but there are plenty more that could have been listed. The reader is for instance referred to [4], [5], [7], [8], [10], [17] and [24] for information on the role of the DPP in different areas of Banach space theory. In this dissertation, however, we are motivated by the two papers [7] and [8] to study alternative Dunford-Pettis properties, to introduce a scale of (new) alternative Dunford-Pettis properties, which we call DP*-properties of order p (briefly denoted by DP*P), and to consider characterisations of Banach spaces with these properties as well as applications thereof to polynomials and holomorphic functions on Banach spaces. In the paper [8] the class Cp(X, Y) of p-convergent operators from a Banach space X to a Banach space Y is introduced. Replacing the requirement that weakly compact operators on X should be completely continuous in the case of the DPP for X (as is mentioned above) by “weakly compact operators on X should be p-convergent", an alternative Dunford-Pettis property (called the Dunford-Pettis property of order p) is introduced. More precisely, if 1 ≤ p ≤ , a Banach space X is said to have DPPp if the inclusion W(X, Y)  Cp(X, Y) holds for all Banach spaces Y . Here W(X, Y) denotes the family of all weakly compact operators from X to Y. We now have a scale of “Dunford-Pettis like properties" in the sense that all Banach spaces have the DPP1, if p < q, then each Banach space with the DPPq also has the DPPp and the strongest property, namely the DPP1 coincides with the DPP. In the paper [7] the authors study a property on Banach spaces (called the DP*-property, or briey the DP*P) which is stronger than the DPP, in the sense that if a Banach space has this property then it also has DPP. We say X has the DP*P, when all weakly compact sets in X are limited, i.e. each sequence (x*n)  X * in the dual space of X which converges weak* to 0, also converges uniformly (to 0) on all weakly compact sets in X. It turns out that this property is equivalent to another property on Banach spaces which is introduced in [17] (and which is called the *-Dunford-Pettis property) as follows: We say a Banach space X has the *-Dunford-Pettis property if for all weakly null sequences (xn) in X and all weak* null sequences (x*n) in X*, we have x*n(xn) n 0. After a thorough study of the DP*P, including characterisations and examples of Banach spaces with the DP*P, the authors in [7] consider some applications to polynomials and analytic functions on Banach spaces. Following an extensive literature study and in depth research into the techniques of proof relevant to this research field, we are able to present a thorough discussion of the results in [7] and [8] as well as some selected (relevant) results from other papers (for instance, [2] and [17]). This we do in Chapter 2 of the dissertation. The starting point (in Section 2.1 of Chapter 2) is the introduction of the so called p-convergent operators, being those bounded linear operators T : X  Y which transform weakly p-summable sequences into norm-null sequences, as well as the so called weakly p-convergent sequences in Banach spaces, being those sequences (xn) in a Banach space X for which there exists an x  X such that the sequence (xn - x) is weakly p-summable. Using these concepts, we state and prove an important characterisation (from the paper [8]) of Banach spaces with DPPp. In Section 2.2 (of Chapter 2) we continue to report on the results of the paper [7], where the DP*P on Banach spaces is introduced. We focus on the characterisation of Banach spaces with DP*P, obtaining among others that a Banach space X has DP*P if and only if for all weakly null sequences (xn) in X and all weak* null sequences (x*n) in X*, we have x*n(xn) n 0. An important characterisation of the DP*P considered in this section is the fact that X has DP*P if and only if every T  L(X, c0) is completely continuous. This result proves to be of fundamental importance in the study of the DP*P and its application to results on polynomials and holomorphic functions on Banach spaces. To be able to report on the applications of the DP*P in the context of homogeneous polynomials and analytic functions on Banach spaces, we embark on a study of “Complex Analysis in Banach spaces" (mostly with the focus on homogeneous polynomials and analytic functions on Banach spaces). This we do in Chapter 3; the content of the chapter is mostly based on work in the books [23] and [14], but also on the work in some articles such as [15]. After we have discussed the relevant theory of complex analysis in Banach spaces in Chapter 3, we devote Chapter 4 to considering properties of polynomials and analytic functions on Banach spaces with DP*P. The discussion in Chapter 4 is based on the applications of DP*P in the paper [7]. Finally, in Chapter 5 of the dissertation, we contribute to the study of “Dunford-Pettis like properties" by introducing the Banach space property “DP*P of order p", or briefly the DP*Pp for Banach spaces. Using the concept “weakly p-convergent sequence in Banach spaces" as is defined in [8], we define weakly-p-compact sets in Banach spaces. Then a Banach space X is said to have the DP*-property of order p (for 1 ≤ p ≤ ) if all weakly-p-compact sets in X are limited. In short, we say X has DP*Pp. As in [8] (where the DPPp is introduced), we now have a scale of DP*P-like properties, in the sense that all Banach spaces have DP*P1 and if p < q and X has DP*Pq then it has DP*Pp. The strongest property DP*P coincides with DP*P. We prove characterisations of Banach spaces with DP*Pp, discuss some examples and then consider applications to polynomials and analytic functions on Banach spaces. Our results and techniques in this chapter depend very much on the results obtained in the previous three chapters, but now we have to find our own correct definitions and formulations of results within this new context. We do this with some success in Sections 5.1 and 5.2 of Chapter 5. Chapter 1 of this dissertation provides a wide range of concepts and results in Banach spaces and the theory of vector sequence spaces (some of them very deep results from books listed in the bibliography). These results are mostly well known, but they are scattered in the literature - they are discussed in Chapter 1 (some with proof, others without proof, depending on the importance of the arguments in the proofs for later use and depending on the detail with which the results are discussed elsewhere in the literature) with the intention to provide an exposition which is mostly self contained and which will be comfortably accessible for graduate students. The dissertation reflects the outcome of our investigation in which we set ourselves the following goals: 1. Obtain a thorough understanding of the Dunford-Pettis property and some related (both weaker and stronger) properties that have been studied in the literature. 2. Focusing on the work in the paper [8], understand the role played in the study of difierent classes of operators by a scale of properties on Banach spaces, called the DPPp, which are weaker than the DP-property and which are introduced in [8] by using the weakly p-summable sequences in X and weakly null sequences in X*. 3. Focusing on the work in the paper [7], investigate the DP*P for Banach spaces, which is the exact property to answer a question of Pelczynsky's regarding when every symmetric bilinear separately compact map X x X  c0 is completely continuous. 4. Based on the ideas intertwined in the work of the paper [8] in the study of a scale of DP-properties and the work in the paper [7], introduce the DP*Pp on Banach spaces and investigate their applications to spaces of operators and in the theory of polynomials and analytic mappings on Banach spaces. Thereby, not only extending the results in [7] to a larger family of Banach spaces, but also to find an answer to the question: “When will every symmetric bilinear separately compact map X x X  c0 be p-convergent?" / Thesis (M.Sc. (Mathematics))--North-West University, Potchefstroom Campus, 2012.

Dans le premier chapitre, nous définissons la notion d’espaces à partitions pondérées qui généralise la structure d’espaces à murs mesurés et qui fournit un cadre géométrique à l’étude des actions isométriques affines sur des espaces de Banach pour les groupes localement compacts à base dénombrable. Dans un premier temps, nous caractérisons les actions isométriques affines propres sur des espaces de Banach en termes d’actions propres par automorphismes sur des espaces à partitions pondérées. Puis, nous nous intéressons aux structures de partitions pondérées naturelles pour les actions de certaines constructions de groupes : somme directe ; produit semi-directe ; produit en couronne et produit libre. Nous établissons ainsi des résultats de stabilité de la propriété PLp par ces constructions. Notamment, nous généralisons un résultat de Cornulier, Stalder et Valette de la façon suivante : le produit en couronne d’un groupe ayant la propriété PLp par un groupe ayant la propriété de Haagerup possède la propriété PLp. Dans le deuxième chapitre, nous nous intéressons aux espaces métriques quasi-médians - une généralisation des espaces hyperboliques à la Gromov et des espaces médians - et à leurs propriétés. Après l’étude de quelques exemples, nous démontrons qu’un espace δ-médian est δ′-médian pour tout δ′ ≥ δ. Ce résultat nous permet par la suite d’établir la stabilité par produit directe et par produit libre d’espaces métriques - notion que nous développons par la même occasion. Le troisième chapitre est consacré à la définition et l’étude d’une distance propre, invariante à gauche et qui engendre la topologie explicite sur les groupes localement compacts, compactement engendrés. Après avoir montré les propriétés précédentes, nous prouvons que cette distance est quasi-isométrique à la distance des mots sur le groupe et que la croissance du volume des boules est contrôlée exponentiellement. / In the first chapter, we define the notion of spaces with labelled partitions which generalizes the structure of spaces with measured walls : it provides a geometric setting to study isometric affine actions on Banach spaces of second countable locally compact groups. First, we characterise isometric affine actions on Banach spaces in terms of proper actions by automorphisms on spaces with labelled partitions. Then, we focus on natural structures of labelled partitions for actions of some group constructions : direct sum ; semi-direct product ; wreath product and free product. We establish stability results for property PLp by these constructions. Especially, we generalize a result of Cornulier, Stalder and Valette in the following way : the wreath product of a group having property PLp by a Haagerup group has property PLp. In the second chapter, we focus on the notion of quasi-median metric spaces - a generalization of both Gromov hyperbolic spaces and median spaces - and its properties. After the study of some examples, we show that a δ-median space is δ′-median for all δ′ ≥ δ. This result gives us a way to establish the stability of the quasi-median property by direct product and by free product of metric spaces - notion that we develop at the same time. The third chapter is devoted to the definition and the study of an explicit proper, left-invariant metric which generates the topology on locally compact, compactly generated groups. Having showed these properties, we prove that this metric is quasi-isometric to the word metric and that the volume growth of the balls is exponentially controlled.

A classificação isomorfa dos espaços de Banach separáveis C(K) é devida a Milutin no caso em que K são não enumeráveis e a Bessaga e Pelczynski no caso em que K são enumeráveis. Neste trabalho apresentamos uma extensão vetorial dessa classificação e tiramos várias consequências, por exemplo, considerando o espaço métrico compacto infinito K e Y um espaço de Banach: &nbsp; &nbsp; 1. Sendo 1 < p < &infin; e &Gamma; um conjunto infinito, classificamos, a menos de isomorfismo, os espaços de Banach C(K, Y &oplus; lp(&Gamma;)), quando o dual de Y contém uma cópia de lq, onde 1/p+ 1/q =1. &nbsp; &nbsp; 2. Classificamos os espaços de Banach C(K, Y &oplus; l&infin;(&Gamma;)), quando a densidade de Y é estritamente menor que 2|&Gamma;|. &nbsp; &nbsp; 3. Classificamos os espaços de Banach C(K &times;(S&oplus; &beta;&Gamma;)) e C(S &oplus; (K&times; &beta;&Gamma;)), onde S é um compacto disperso de Hausdorff arbitrário e &beta;&Gamma; é a compactificação de Stone-Cech de &Gamma;. Obtemos, também, algumas leis de cancelamento para espaços de Banach da forma C(K1,X)&oplus; C(K2,Y), onde K1 e K2 são espaços compactos métricos infinitos de Hausdorff e X, Y espaços de Banach satisfazendo condições adequadas. Estabelecemos também um teorema de quase-dicotomia envolvendo os espaços C(K,X), onde X tem cotipo finito. Finalmente, apresentamos algumas majorações nas distorções de isomorfismos positivos de C([0,&omega;k]) em C([0,&omega;]) e também de C([0,&omega;]) em C([0,&omega;k]), k&isin; N, k &ge; 2. / The isomorphic classification of separable Banach spaces C(K) is due Milutin in the case when K are uncountable and to Bessaga and Pelczynski in the case when K are countable. In this work we prove a vectorial extention of this classification and provide several consequences, for example considering the infinite metric compact space K and Y a Banach space: &nbsp; &nbsp; 1. Let 1 < p < &infin; and &Gamma; a infinite set, we classify, up to an isomorphism, the Banach spaces C(K, Y &oplus; lp(&Gamma;)), in the case where the dual of Y contains no copy of lq, where 1/p+ 1/q =1. &nbsp; &nbsp; 2. We classify the Banach spaces C(K, Y &oplus; l&infin;(&Gamma;)), when the density character of Y is strictly less that 2|&Gamma;|. &nbsp; &nbsp; 3. We classify the Banach spaces C(K &times;(S&oplus; &beta;&Gamma;)) and C(S &oplus; (K&times; &beta;&Gamma;)) where S is an arbitrary dispersed compact and &beta;&Gamma; is the Stone-Cech compactification of &Gamma;. We obtain also some cancellation laws for Banach spaces in the form C(K1,X)&oplus; C(K2,Y), where K1 and K2 are metric compact Hausdorff spaces and X, Y Banach spaces satisfying appropriate conditions. We established also a quasi-dichotomy theorem envolving the C(K,X) spaces, where X is of finite cotype. Finally, we present some upper bounds of distortions of positive isomorphisms of C([0,&omega;k]) on C([0,&omega;]) and also of C([0,&omega;]) on C([0,&omega;k]), k&isin; N, k &ge; 2.

Viele Probleme der Riss- und Bruchmechanik sowie der mathematischen Physik lassen sich auf Lösungen von singulären Integralgleichungen über einem Intervall zurückführen. Diese Gleichungen setzen sich im Wesentlichen aus dem Cauchy'schen singulären Integraloperator und zusätzlichen Integraloperatoren mit festen Singularitäten in den jeweiligen Kernen zusammen. Zur numerischen Lösung solcher Gleichungen werden polynomiale Kollokations-Quadraturverfahren betrachet. Als Ansatzfunktionen und Kollokationspunkte werden dabei gewichtete Polynome und Tschebyscheff-Knoten gewählt. Die Gewichte sind so gewählt, dass diese das asymptotische Verhalten der Lösung in den Randpunkten widerspiegeln. Mit Hilfe von C*-Algebra Techniken, werden in dieser Arbeit notwendige und hinreichende Bedingungen für die Stabilität der Kollokations-Quadraturverfahren angegeben. Die theoretischen Resultate werden dabei durch numerische Berechnungen anhand des Problems der angerissenen Halbebene und des angerissenen Loches überprüft.

[ES] El objetivo de esta tesis es estudiar distintas propiedades de los operadores de composición ponderados en diferentes espacios ponderados de funciones analíticas. Dado un peso v estrictamente positivo y continuo en el disco complejo, consideramos unos ciertos espacios de Banach de funciones analíticas en el discto complejo. Estos espacios son los conjuntos de las funciones holomorfas en el disco f tales que el supremo, de los z en el disco, de v(z)|f(z)| es finito. También consideramos los espacios de las funciones holorfas f que cumplen que v(z)|f(z)| tiende a cero cuando |z| se acerca a 1. Dada una sucesión de pesos, trabajamos con los espacios formados por las intersecciones y uniones de los espacios de Banach ponderados determinados por los pesos de la sucesión. El espacio resultante de la intersección es un espacio de Fréchet y es el límite proyectivo de los espacios de Banach citados. Este espacio está provisto de la topología del límite proyectivo. El espacio resultante de la unión es un espacio LB (límite de Banach), y es el límite inductivo de los espacios citados, con la topología del límite inductivo. Cuando la sucesión de pesos viene determinada por los pesos (1-|z|)^n con n natural, el espacio resultante de la unión se llama espacio de Korenblum, que también es un límite inductivo. En la tesis estudiamos la continuidad, compacidad e invertibilidad de los operadores de composición ponderados en los espacios descritos arriba. También estudiamos algunas propiedades de su espectro y de su espectro puntual. / [CA] L'objectiu d'aquesta tesi és estudiar distintes propietats dels operadors de composició ponderats en diferents espais ponderats de funcions analítiques. Donat un pes v estrictament positiu i continu en el disc del pla complex, considerem uns certs espais de Banach de funcions analítiques en el disc complex. Aquests espais són els conjunts de les funcions holomorfes en el disc f tals que el suprem, dels z en el disc, de v(z)|f(z)| és finit. També considerem els espai de les funcions que verifiquen que v(z)|f(z)| tendeix a zero quan |z| s'apropa a 1. Donada una successió de pesos, treballem amb els espais formats per les interseccions i unions dels espais de Banach ponderats determinats pels pesos de la successió. L'espai resultant de la intersecció és un espai de Fréchet, i és el límit projectiu dels espais de Banach esmentats. Aquest espai està prove ̈ıt de la topologia del l ́ımit projectiu. L'espai resultant de la unió és un espai LB (límit de Banach), i és el límit inductiu dels espais esmentats, amb la topologia del límit inductiu. Quan la successió de pesos està determinada pels pesos (1-|z|)^n amb n natural, l'espai resultant de la unió s'anomena espai de Korenblum, que també és un límit inductiu. En al tesi estudiem la continu ̈ıtat, , compacitat i invertibilitat de l'operador de composició ponderat en els espais descrits abans. També estudiem algunes propietats del seu espectre i del seu espectre puntual. / [EN] The aim of this thesis is to study some properties of the weighted composition operators on different weighted spaces of analytic functions. Given a weight v strictly positive and continuous on the complex disc, we consider certain Banach spaces of analytic functions on the complex disc. These spaces are the sets of the holomorphic functions on the disc f such that the supremum, when z is in the disc, of v(z)|f(z)| is finite. We also consider the spaces of the holomorphic functions f such that v(z)|f(z)| tends to 0 whenever |z| goes to 1. Given a sequence of weights, we work with the spaces described by the intersection or union of the weighted Banach spaces determined by the weights in the sequence. The space of the intersection is a Fréchet space and it is the projective limit of the mentioned Banach spaces. This space is endowed with the projective limit topology. The space given by the union is an LB-space (limit of Banach), and it is the inductive limit of the mentioned spaces, with the inductive limit topology. When the sequence is given by the weights (1-|z|)^n with n natural, the space of the union is called Korenblum space, which is also an inductive limit. In the thesis we study the continuity, compactness and invertibility of the weighted composition operators on the spaces described above. We also study some properties of the spectrum and point spectrum. / Gomez Orts, E. (2022). Weighted Composition Operators on Spaces of Analytic Functions [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/183028

[ES] Desde el comienzo de la Teoría de Espacios de Banach, el estudio de los subespacios complementados y no complementados ha sido uno de los principales temas del área. Específicamente, en espacios de Banach no separables, han habido grandes esfuerzos en construir un marco teórico para describir la estructura de subespacios linealmente complementados en espacios de Banach. Concepctos clásicos como la Propiedad del Complemento Separable, Resoluciones Proyectivas de la Identidad, y la Propiedad de Plichko han sido y continúan siendo estudiadas en esta disciplina. En igual medida, las aplicaciones de Lipschitz en espacios de Banach también han jugado un papel importante en el desarrollo de la teoría. Cuestiones como la clasificación de Lipschitz de los espacios de Banach, la diferenciabilidad de las funciones de Lipschitz, o la existencia de retracciones de Lipschitz a subconjuntos y subespacios de espacios de Banach, son líneas de investigación activas con abundantes resultados y aplicaciones. En esta tesis analizamos la estructura de retractos de Lipschitz en espacios métricos y espacios de Banach no separables, de forma análoga a la teoría de complementación lineal en espacios de Banach. También discutimos la conexión de este tema con el progreso actual en el estudio de la estructura de los espacios de Lipschitz-free, y con el problema de la existencia de operadores de extensión lineales para funciones de Lipschitz. En primer lugar, generalizamos algunas herramientas clásicas de la teoría lineal al marco no lineal: Definimos el concepto de esqueletos retractivos de Lipschitz como una generalización a los esqueletos proyectivos. Como aplicación de estas nociones, demostramos que el espacio de Lipschitz-free asociado a un espacio de Banach con la propiedad de Plichko tiene a su vez la propiedad de Plichko. Utilizamos también los esqueletos retractivos de Lipschitz para caracterizar aquellos espacios métricos cuyo espacio de Lipschitz-free tiene la propiedad de Plichko con medidas de Dirac, y mostramos que el espacio de Lipschitz-free asociado a cualquier R-árbol es 1-Plichko con moléculas elementales. A continuación, pasamos a definir la Propiedad del Retracto de Lipschitz (α, β) (o la Lipschitz RP(α, β)) para un par de cardinales infinitos α ≤ β. Esta es la propiedad no lineal análoga a la clásica Propiedad del Complemento. Observamos que los espacios C(K) tiene la Lipschitz RP(ℵ0, ℵ0), lo cual implica que sus espacios de Lipschitz-free asociados poseen la Propiedad del Complemento Separable. Siguiendo con el estudio previo, construimos, para cada cardinal infinito Λ, un espacio métrico completo sin la Lipschitz RP(Λ, Λ)). En el caso numerable, podemos mejorar este resultado produciendo un espacio métrico completo que satisface una propiedad más fuerte que la negación de la Lipschitz RP(ℵ0, ℵ0): Todo subconjunto separable con almenos dos puntos no es un retracto de Lipschitz. Finalmente, generalizamos un resultado de Heinrich y Mankiewicz al marco no lineal al mostrar que en cada espacio métrico M, todo subconjunto está contenido en otro subconjunto con el mismo carácter de densidad que además admite un operador lineal de extensión de funciones Lipschitz. / [CA] Des del principi de la Teoria d'Espais de Banach, l'estudi dels subespais complementats i no complementats ha estat un dels principals temes de l'àrea. Específicament, en espais de Banach no separables, hi ha hagut un gran esforç de construir un marc teòric per descriure l'estructura de subespais linealment complementats en espais de Banach. Conceptes clàssics com la Propietat del Complement Separable, Resolucions Projectives de la Identitat, i la Propietat de Plichko han estat i continuen sent estudiades en aquesta disciplina. En igual mesura, les aplicacions de Lipschitz en espais de Banach també han jugat un paper important en el desenvolupament de la teoria. Qüestions com la classificació de Lipschitz dels espais de Banach, la diferenciabilitat de les funcions de Lipschitz, o l'existència de retraccions de Lipschitz a subconjunts i subespais d'espais de Banach, són línies d'investigació actives amb abundants resultats i aplicacions. En aquesta tesi analitzem l'estructura de retractes de Lipschitz en espais mètrics i espais de Banach no separables, de manera anàloga a la teoria de complementació lineal en espais de Banach. També discutim la connexió d'aquest tema amb el progrés actual en l'estudi de l'estructura dels espais de Lipschitz-free, i amb el problema de l'existència d'operadors d'extensió lineals per a funcions de Lipschitz. En primer lloc, generalitzem algunes eines clàssiques de la teoria lineal al marc no lineal: Definim el concepte d'esquelets retractius de Lipschitz com una generalització dels esquelets projectius. Com aplicació d'aquestes nocions, demostrem que l'espai de Lipschitz-free associat a un espai de Banach amb la propietat de Plichko té la propietat de Plichko. Utilitzem també els esquelets retractius de Lipschitz per a caracteritzar aquells espais mètrics que generen espais de Lipschitz-free amb la propietat de Plichko amb mesures de Dirac, i mostrem que l'espai de Lipschitz-free associat a qualsevol R-arbre és 1-Plichko amb molècules elementals. A continuació, passem a definir la Propietat del Retracte de Lipschitz (α, β) (o la Lipschitz RP(α, β)) per a un parell de cardinals infinits α ≤ β. Aquesta és la propietat no lineal anàloga a la clàssica Propietat del Complement. Observem que els espais C(K) tenen la Lipschitz RP(ℵ0, ℵ0), la qual cosa implica que els espais de Lipschitz-free associats posseeixen la Propietat del Complement Separable. Seguint amb l'estudi previ, construïm, per a cada cardinal infinit Λ, un espai mètric complet sense la Lipschitz RP(Λ, Λ). En el cas numerable, podem millorar aquest resultat produint un espai mètric complet que satisfà una propietat més forta que la negació de la Lipschitz RP(ℵ0, ℵ0): Tot subconjunt separable amb almenys dos punts no és un retracte de Lipschitz. Finalment, generalitzem un resultat de Heinrich i Mankiewicz al marc no lineal al demostrar que en cada espai mètric M, tot subconjunt està contingut en altre subconjut amb el mateix caràcter de densitat que a més admet un operador lineal d'extensió de funcions Lipschitz. / [EN] Since the inception of Banach Space Theory, the study of complemented and uncomplemented subspaces of Banach spaces has been one of the main themes of the area. Specifically, in non-separable Banach spaces, there have been many efofrts in constructing a theoretical framework to describe the linear complementation structure of Banach spaces. Classical concepts such as the Separable Complementation Property, Projectional Resolutions of the Identity, and the Plichko Property have been and continue to be studied in this area. Similarly, Lipschitz maps between Banach spaces have also played a main role in the development of the theory. Questions such as the Lipschitz classification of Banach spaces, difefrentiability of Lipschitz maps, or the existence of Lipschitz retractions onto subsets and subspaces of Banach spaces, have been and continue to be active topics of research with a wealth of results and applications. In this thesis we analyse the Lipschitz retractional structure of non-separable metric and Banach spaces, as an analogous theory to the linear complementation one in Banach spaces. We also discuss the connection of this topic with the ongoing program to study the structure of Lipschitz-free Banach spaces, and to the problem of finding bounded linear extension operators for Lipschitz functions. First, we generalize some classical tools of the linear theory to the non-linear setting: We define the concept of Lipschitz retractional skeletons as a generalization of Projectional skeletons. As applications of these concepts, we show that the Lipschitz-free space of a Plichko Banach space is again Plichko. We also use Lipschitz retractional skeletons to characterize metric spaces whose Lipschitz-free spaces enjoy the Plichko property witnessed by Dirac measures, and we show that the Lipschitz-free space of any R-tree is 1-Plichko witnessed by molecules. Next, we pass on to defining the (α, β) Lipschitz Retraction Property (Lipschitz RP(α, β) for short) for a pair of infinite cardinals α ≤ β. These are the non-linear analogues to the classical Complementation Properties. We observe that C(K) spaces enjoy the Lipschitz RP(ℵ0, ℵ0), which in turn implies that their associated Lipschitz-free space satisfy the Separable Complementation Property. As a continuation of the previous study, we construct, for every infinite cardinal Λ, a complete metric space which fails the Lipschitz RP(Λ, Λ). In the countable case, we are able to produce a complete metric space, called the skein space, with a stronger property than the negation of the Lipschitz RP(ℵ0, ℵ0): Every separable subset of the skein space with at least two points fails to be a Lipschitz retract. Finally, we generalize a result of Heinrich and Mankiewicz to the non-linear setting, by showing that for any metric space M, every subset is contained in another subset of the same density character which admits a bounded linear extension operator for the space of Lipschitz functions. / Quilis Sandemetrio, A. (2023). Lipschitz Structure of Metric and Banach Spaces [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/200447