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Baire and Harmonic Functions
Pošta, Petr ; Lukeš, Jaroslav (advisor)
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...
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Baire and Harmonic Functions
Pošta, Petr ; Lukeš, Jaroslav (advisor) ; Benyaiche, Allami (referee) ; Netuka, Ivan (referee)
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...
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Riemann type integral in Banach spaces
Mrhal, Filip ; Lukeš, Jaroslav (advisor) ; Zajíček, Luděk (referee)
Title: Riemann type integral in Banach spaces Author: Filip Mrhal Department: Department of Mathematical Analysis Supervisor: Prof. RNDr. Jaroslav Lukeš, DrSc., Department of Mathematical Analysis Abstract: In this thesis we study some differences in the behaviours of the Ri- emann integral when integrating functions from any compact subinterval of real numbers to real numbers or to any Banach space. Especially, we outline that the Lebesgue theorem is no longer valid in relationship to functions with images in some Banach spaces. We show that for some well-known Banach spaces using counterexamples. Keywords: Riemann integral, Banach space, Lebesgue theorem 1
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Geometric linear and nonlinear problems of function spaces
Petráček, Petr ; Lukeš, Jaroslav (advisor) ; Aron, Richard M. (referee) ; Bobok, Jozef (referee)
Název práce: Geometrické lineární a nelineární problémy prostor· funkcí Autor: Petr Petráček Katedra: Katedra matematické analýzy 'kolitel: prof. RNDr. Jaroslav Lukeš, DrSc., Katedra matematické analýzy Abstrakt: Tato práce sestává ze čtyř vědeckých článk·. lánky prezentované v prvních dvou kapitolách se věnují teorii reálných a komplexních L1-preduál·. lánky prezentované v třetí a čtvrté kapitole jsou věnovány problematice line- ability a algebrability podmnožin reálných funkcí a měr. V Kapitole 1 předsta- vujeme charakterizaci komplexních L1-preduál· pomocí komplexního barycent- rického zobrazení. Tato charakterizace je přirozeným rozšířením charakterizace reálných L1 preduál· pocházející od Bednara a Laceyho. V Kapitole 2 odpoví- dáme na otázku položenou Laceym v roce 1973. Dokazujeme přitom existenci kompaktního prostoru K a uzavřeného podprostoru H ⊂ C(K) obsahujícího kon- stantní funkce, pro který platí ∂HK = K, H je maximální vzhledem k ∂HK a H není L1-preduál. V Kapitole 3 se věnujeme lineabilitě množin nikde mono- tonních znaménkových Radonových měr na Rd . Konkrétně dokazujeme existence vektorového prostoru dimenze c jehož každý nenulový prvek je nikde monotonní míra absolutně spojitá vzhledem k d-rozměrné Lebesgueově míře. Nadto dokazu- jeme, že existuje takový lineární prostor, který je hustý...
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Choquet Theory and Dirichlet Problem
Omasta, Eduard ; Lukeš, Jaroslav (advisor) ; Brzezina, Miroslav (referee) ; Medková, Dagmar (referee)
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.
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Microscopic sets and drops in Banach spaces
Pospíšil, Marek ; Lukeš, Jaroslav (advisor) ; Fabian, Marián (referee)
First we define microscopic sets on the real axis and study their relation to the sets of Hausdorff and Lebesgue measure zero and the sets of first category. In the second part, we prove the Bishop-Phelps' theorem and its equivalence with the Ekeland's variational principle, the Daneš's drop theorem, the Brézis-Browder's theorem and the Caristi-Kirks's theorem. Doing so we define the notion of a drop as the convex hull of a set and a point. In the third part we prove that the drop property equals reflexivity in some sense. A space has the drop property if it is possible to find the drop from the Daneš's theorem even in a more general case than the theorem itself guarantees. Furthermore, we characterize this property using the approximative compactness. Last, we study the microscopic drop property that is more relaxed than the original drop property. We find out that those two notions are for noncompact sets in reflexive spaces equivalent. Powered by TCPDF (www.tcpdf.org)
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Microscopic sets and drops in Banach spaces
Pospíšil, Marek ; Lukeš, Jaroslav (advisor) ; Zelený, Miroslav (referee)
First we define microscopic sets on the real axis and study their relation to the sets of Hausdorff and Lebesgue measure zero and the sets of first category. In the second part, we prove the Ekeland's variational principle and its equivalence with the the Daneš's drop theorem, the Brézis-Browder's theorem, the Phelps' lemma and the Caristi-Kirks's theorem. Furthermore, we discuss its relation to the Bishop-Phelps' theorem. Doing so we define the notion of a drop as the convex hull of a set and a point. In the third part we prove that the drop property equals reflexivity in some sense. A space has the drop property if it is possible to find the drop from the Daneš's theorem even in a more general case than the theorem itself guarantees. Furthermore, we characterize this property using the approximative compactness. Last, we study the microscopic drop property that is more relaxed than the original drop property. We find out that those two notions are for certain sets in reflexive spaces equivalent.
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Geometric properties of subspaces of continuous functions
Petráček, Petr ; Lukeš, Jaroslav (advisor) ; Netuka, Ivan (referee)
In this thesis we study certain geometric properties of Müntz spa- ces as subspaces of continuous functions. In the first chapter we present some of the most important examples of the Müntz type theorems. Namely, we present the classic Müntz theorem and the Full Müntz theorem in the setting of the space of continuous functions on the interval [0, 1]. We also mention several extensions of these theorems to the case of continuous functions on the general interval [a, b] as well as an analogy of the Full Müntz theorem for the Lp ([0, 1]) spaces. The second chapter is divided into three sections. In the first section we present some definitions and well-known theorems of Choquet theory, which we use to characterize the Choquet boundary of Müntz spa- ces. In the second section we present the result concerning non-reflexivity of Müntz spaces as well as its corollary describing the non-existence of an equiva- lent uniformly convex norm on these spaces. In the third section, we concern ourselves with the question of Müntz spaces having the Radon-Nikodym pro- perty. As a main result of this part we show that a certain type of Müntz spaces doesn't have the Radon-Nikodym property. The final chapter contains a summary of some known results as well as open problems related to the theory of Müntz spaces....
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Some results in convexity and in Banach space theory
Kraus, Michal ; Lukeš, Jaroslav (advisor) ; Kalenda, Ondřej (referee) ; Smith, Richard (referee)
This thesis consists of four research papers. In the first paper we construct nonmetrizable compact convex sets with pathological sets of simpliciality, show- ing that the properties of the set of simpliciality known in the metrizable case do not hold without the assumption of metrizability. In the second paper we construct an example concerning remotal sets, answering thus a question of Martín and Rao, and present a new proof of the fact that in every infinite- dimensional Banach space there exists a closed convex bounded set which is not remotal. The third paper is a study of the relations between polynomials on Banach spaces and linear identities. We investigate under which conditions a linear identity is satisfied only by polynomials, and describe the space of poly- nomials satisfying such linear identity. In the last paper we study the coarse and uniform embeddability between Orlicz sequence spaces. We show that the embeddability between two Orlicz sequence spaces is in most cases determined only by the values of their upper Matuszewska-Orlicz indices. 1
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