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Noncommutative Choquet theory
Šišláková, Jana ; Spurný, Jiří (advisor) ; Hamhalter, Jan (referee)
- ABSTRACT - Noncommutative Choquet theory Let S be a linear subspace of a commutative C∗ -algebra C(X) that se- parates points of C(X) and contains identity. Then the closure of the Choquet boundary of the function system S is the Šilov boundary relati- ve to S. In the case of a noncommutative unital C∗ -algebra A, consider S a self-adjoint linear subspace of A that contains identity and generates A. Let us call S operator system. Then the noncommutative formulation of the stated assertion is that the intersection of all boundary representa- tions for S is the Šilov ideal for S. To that end it is sufficient to show that S has sufficiently many boundary representations. In the present work we make for the proof of that this holds for separable operator system.
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Quantitative properties of Banach spaces
Krulišová, Hana ; Kalenda, Ondřej (advisor) ; Raja Baño, Matias (referee) ; Hamhalter, Jan (referee)
The present thesis consists of four research papers. Each article deals with quan- tifications of certain properties of Banach spaces. The first paper is devoted to the Grothendieck property. The main result is that the space ∞ enjoys its quan- titative version. The second paper investigates quantifications of the Banach- Saks and the weak Banach-Saks property. The relationship of compact, weakly compact, Banach-Saks, and weak Banach-Saks sets is quantified, as well as some characterizatons of weak Banach-Saks sets. In the third article we discuss possible quantifications of Pelczy'nski's property (V), their characterizations and relations to quantitative versions of other properties of Banach spaces. The last paper is a continuation of the third one. We prove that C∗ -algebras have a quantita- tive version of the property (V), which generalizes one of the results obtained in the previous paper. Moreover, we establish a relationship between quantita- tive versions of the property (V) and the Grothendieck property in dual Banach spaces. 1
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Integral representation of operator algebras
Penk, Tomáš ; Spurný, Jiří (advisor) ; Hamhalter, Jan (referee)
By a representation of a C*-algebra A on a Hilbert space H we mean a morphism : A → L(H). After summing up neccessary knowledge from the theory of Banach and Hilbert spaces and C*-al- gebras we show that for every C*-algebra a representation exists. We describe its structure detiledly and we focus on examining cyclic representations. We find out that cyclic representations relate to the state space. Because every state can be expressed as an integral with respect to an appropriate measure on the states, in is possible to assign a measure on the state space to each cyclic represen- tation. Therefore, we investigate connexion of a representation with this measure as same as with the corresponding state. This leads us to the definition of an orthogonal measure. We find out that its properties relate with certain subalgebras of L(H). At the end we show that for a separable C*-algebra it is possible to express a representation fulfilling suitable assumptions in the form of a direct integral. 1
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Noncommutative Choquet theory
Šišláková, Jana ; Spurný, Jiří (advisor) ; Hamhalter, Jan (referee)
- ABSTRACT - Noncommutative Choquet theory Let S be a linear subspace of a commutative C∗ -algebra C(X) that se- parates points of C(X) and contains identity. Then the closure of the Choquet boundary of the function system S is the Šilov boundary relati- ve to S. In the case of a noncommutative unital C∗ -algebra A, consider S a self-adjoint linear subspace of A that contains identity and generates A. Let us call S operator system. Then the noncommutative formulation of the stated assertion is that the intersection of all boundary representa- tions for S is the Šilov ideal for S. To that end it is sufficient to show that S has sufficiently many boundary representations. In the present work we make for the proof of that this holds for separable operator system.
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