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1
Ordonez-Delgado, Bartleby. "Algebras of Toeplitz Operators." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/32378.
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In this work we examine C*-algebras of Toeplitz
operators over the unit ball in
C^n and the unit polydisc in C^2. Toeplitz
operators are interesting examples of non-normal operators that
generate non-commutative C*-algebras. Moreover, in the nice
cases (depending on the geometry of the domain) of algebras of
Toeplitz operators we can recover some analogues of the spectral
theorem up to compact operators. In this setting, we can capture
the index of a Fredholm operator which is a fundamental numerical
invariant in Operator Theory.Master of Science
2
Fedchenko, Dmitry, and Nikolai Tarkhanov. "An index formula for Toeplitz operators." Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7249/.
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We prove a Fedosov index formula for the index of Toeplitz operators connected with the Hardy space of solutions to an elliptic system of first order partial differential equations in a bounded domain of Euclidean space with infinitely differentiable boundary.
3
Deleporte-Dumont, Alix. "Low-energy spectrum of Toeplitz operators." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD004/document.
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Les opérateurs de Berezin--Toeplitz permettent de quantifier des fonctions, ou des symboles, sur des variétés kähleriennes compactes, et sont définies à partir du noyau de Bergman (ou de Szeg\H{o}). Nous étudions le spectre des opérateurs de Toeplitz dans un régime asymptotique qui correspond à une limite semiclassique. Cette étude est motivée par le comportement magnétique atypique observé dans certains cristaux à basse température. Nous étudions la concentration des fonctions propres des opérateurs de Toeplitz, dans des cas où les effets sous-principaux (du même ordre que le paramètre semiclassique) permet de différencier entre plusieurs configurations classiques, un effet connu en physique sous le nom de sélection quantique Nous exhibons un critère général pour la sélection quantique et nous donnons des développements asymptotiques précis de fonctions propres dans le cas Morse et Morse--Bott, ainsi que dans un cas dégénéré. Nous développons également un nouveau cadre pour le traitement du noyau de Bergman et des opérateurs de Toeplitz en régularité analytique. Nous démontrons que le noyau de Bergman admet un développement asymptotique, avec erreur exponentiellement petite, sur des variétés analytiques réelles. Nous obtenons aussi une précision exponentiellement fine dans les compositions et le spectre d'opérateurs à symbole analytique, et la décroissance exponentielle des fonctions propresBerezin-Toeplitz operators allow to quantize functions, or symbols, on compact Kähler manifolds, and are defined using the Bergman (or Szeg\H{o}) kernel. We study the spectrum of Toeplitz operators in an asymptotic regime which corresponds to a semiclassical limit. This study is motivated by the atypic magnetic behaviour observed in certain crystals at low temperature. We study the concentration of eigenfunctions of Toeplitz operators in cases where subprincipal effects (of same order as the semiclassical parameter) discriminate between different classical configurations, an effect known in physics as quantum selection . We show a general criterion for quantum selection and we give detailed eigenfunction expansions in the Morse and Morse-Bott case, as well as in a degenerate case. We also develop a new framework in order to treat Bergman kernels and Toeplitz operators with real-analytic regularity. We prove that the Bergman kernel admits an expansion with exponentially small error on real-analytic manifolds. We also obtain exponential accuracy in compositions and spectra of operators with analytic symbols, as well as exponential decay of eigenfunctions
4
Fedchenko, Dmitry, and Nikolai Tarkhanov. "A Class of Toeplitz Operators in Several Variables." Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6893/.
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We introduce the concept of Toeplitz operator associated with the Laplace-Beltrami operator on a compact Riemannian manifold with boundary. We characterise those Toeplitz operators which are Fredholm, thus initiating the
index theory.
5
Vasaturo, Anthony P. Vasaturo. "Invertibility of Toeplitz Operators via Berezin Transforms." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1529951538729292.
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Gaebler, David. "Toeplitz Operators on Locally Compact Abelian Groups." Scholarship @ Claremont, 2004. https://scholarship.claremont.edu/hmc_theses/163.
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Given a function (more generally, a measure) on a locally compact Abelian group, one can define the Toeplitz operators as certain integral transforms of functions on the dual group, where the kernel is the Fourier transform of the original function or measure. In the case of the unit circle, this corresponds to forming a matrix out of the Fourier coefficients in a particular way. We will study the asymptotic eigenvalue distributions of these Toeplitz operators.
7
Schulze, Bert-Wolfgang, and Nikolai Tarkhanov. "Boundary value problems with Toeplitz conditions." Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2009/2983/.
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We describe a new algebra of boundary value problems which contains Lopatinskii elliptic as well as Toeplitz type conditions. These latter are necessary, if an analogue of the Atiyah-Bott obstruction does not vanish. Every elliptic operator is proved to admit up to a stabilisation elliptic conditions of such a kind. Corresponding boundary value problems are then Fredholm in adequate scales of spaces. The crucial novelty consists of the new type of weighted Sobolev spaces which serve as domains of pseudodifferential operators and which fit well to the nature of operators.
8
Ordonez-Delgado, Bartleby. "An Embedded Toeplitz Problem." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/29007.
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In this work we investigate multi-variable Toeplitz operators and their relationship with KK-theory in order to apply this relationship to define and analyze embedded Toeplitz problems. In particular, we study the embedded Toeplitz problem of the unit disk into the unit ball in C^2. The embedding of Toeplitz problems suggests a way to define Toeplitz operators over singular spaces.Ph. D.
9
Nikpour, Mehdi. "Toeplitzness of Composition Operators and Parametric Toeplitzness." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1346951238.
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Ehrhardt, Torsten. "Factorization theory for Toeplitz plus Hankel operators and singular integral operators with flip." Doctoral thesis, [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972573305.
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Browning, Brian L. "Time and frequency domain scattering for the one-dimensional wave equation /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/5788.
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Subedi, Krishna Subedi. "Hyponormality and Positivity of Toeplitz operators via the Berezin transform." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1532963068992661.
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Tattersall, Joshua Malcolm. "Toeplitz and Hankel operators on Hardy spaces of complex domains." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/11498/.
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The major focus is on the Hardy spaces of the annulus {z : s < |z| < 1}, with the measure on the boundary being Lebesgue measure normalised such that each boundary has weight 1. There is also consideration of higher order annuli, the Bergmann spaces and slit domains. The focus was on considering analogues of classical problems in the disc in multiply connected regions. Firstly, a few factorisation results are established that will assist in later chapters. The Douglas-Rudin type factorisation is an analogue of factorisation in the disc, and the factorisation of H1 into H2 functions are analogues of factorisation in the disc, whereas the multiplicative factorisation is specific to multiply connected domains. The Douglas-Rudin type factorisation is a classical result for the Hardy space of the disc, here it is shown for the domain {z : s < |z| < 1}. A previous factorisation for H1 into H2 functions exists in [4], an improved constant not depending on s is found here. We proceed to investigate real-valued Toeplitz operators in the annulus, focusing on eigenvalues and eigenfunctions, including for higher order annuli, and amongst other results the general form of an eigenfunction is determined. A paper of Broschinski [10] details the same approach for the annulus {z : s < |z| < 1} as here, but does not consider higher genus settings. There exists work such as in [6] and [5] detailing an alternative approach to eigenvalues in a general setting, using theta-functions, and does not detail the eigenfunctions. After this, kernels of a more general symbol are considered, compared to the disc, and Dyakanov’s theorem from the disc is extended for the annulus. Hankel operators are also considered, in particular with regards to optimal symbols. Finally, analogues of results from previous chapters are considered in the Bergman space, and the Hardy space of a slit annulus.
14
Kraemer, Daniel [Verfasser], and Jörg [Akademischer Betreuer] Eschmeier. "Toeplitz operators on Hardy spaces / Daniel Kraemer ; Betreuer: Jörg Eschmeier." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1209947455/34.
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Ballard, Grey M. "Asymptotic behavior of the eigenvalues of Toeplitz integral operators associated with the Hankel transform." Electronic thesis, 2008. http://dspace.zsr.wfu.edu/jspui/handle/10339/221.
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Vasilyev, Vladimir. "Invertibility of a Class of Toeplitz Operators over the Half Plane." Doctoral thesis, Universitätsbibliothek Chemnitz, 2007. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200700157.
Full textAbstract:
This dissertation is concerned with invertibility and
one-sided invertibility of Toeplitz operators
over the half plane whose generating functions
admit homogenous discontinuities, and with
stability of their pseudo finite sections.
The invertibility criterium is given in terms
of invertibility of a family of one
dimensional Toeplitz operators with piecewise
continuous generating functions. The one-sided
invertibility criterium is given it terms of
constraints on the partial indices of certain
Toeplitz operator valued function.
17
Vasil'ev, Vladimir A. "Invertibility of a class of Toeplitz operators over the half plane." [S.l. : s.n.], 2007.
Find full text
18
Fulsche, Robert [Verfasser]. "Toeplitz operators and generated algebras on non-Hilbertian spaces / Robert Fulsche." Hannover : Gottfried Wilhelm Leibniz Universität, 2020. http://d-nb.info/1223090264/34.
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Yousef, Abdelrahman F. "Two problems in the theory of Toeplitz operators on the Bergman space /." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1242219617.
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Schulze, Bert-Wolfgang. "Toeplitz operators, and ellipticity of boundary value problems with global projection conditions." Universität Potsdam, 2003. http://opus.kobv.de/ubp/volltexte/2008/2651/.
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Ellipticity of (pseudo-) differential operators A on a compact manifold X with boundary (or with edges) Y is connected with boundary (or edge) conditions of trace and potential type, formulated in terms of global projections on Y together with an additional symbolic structure. This gives rise to operator block matrices A with A in the upper left corner. We study an algebra of such operators, where ellipticity is equivalent to the Fredhom property in suitable scales of spaces: Sobolev spaces on X plus closed subspaces of Sobolev spaces on Y which are the range of corresponding pseudo-differential projections. Moreover, we express parametrices of elliptic elements within our algebra and discuss spectral boundary value problems for differential operators.
21
Yousef, Abdelrahman Fawzi. "Two Problems in the Theory of Toeplitz Operators on the Bergman Space." University of Toledo / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1242219617.
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Kou, Kit Ian. "Fast transform based operators for Toeplitz systems and their applications in image restoration." Thesis, University of Macau, 1999. http://umaclib3.umac.mo/record=b1446619.
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Schillo, Dominik Tobias [Verfasser], and Jörg [Akademischer Betreuer] Eschmeier. "K-contractions and perturbations of Toeplitz operators / Dominik Tobias Schillo ; Betreuer: Jörg Eschmeier." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2018. http://d-nb.info/1175950130/34.
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Schillo, Dominik Tobias Verfasser], and Jörg [Akademischer Betreuer] [Eschmeier. "K-contractions and perturbations of Toeplitz operators / Dominik Tobias Schillo ; Betreuer: Jörg Eschmeier." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:291--ds-275628.
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Webb, Marcus David. "Isospectral algorithms, Toeplitz matrices and orthogonal polynomials." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/264149.
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An isospectral algorithm is one which manipulates a matrix without changing its spectrum. In this thesis we study three interrelated examples of isospectral algorithms, all pertaining to Toeplitz matrices in some fashion, and one directly involving orthogonal polynomials. The first set of algorithms we study come from discretising a continuous isospectral flow designed to converge to a symmetric Toeplitz matrix with prescribed eigenvalues. We analyse constrained, isospectral gradient flow approaches and an isospectral flow studied by Chu in 1993. The second set of algorithms compute the spectral measure of a Jacobi operator, which is the weight function for the associated orthogonal polynomials and can include a singular part. The connection coefficients matrix, which converts between different bases of orthogonal polynomials, is shown to be a useful new tool in the spectral theory of Jacobi operators. When the Jacobi operator is a finite rank perturbation of Toeplitz, here called pert-Toeplitz, the connection coefficients matrix produces an explicit, computable formula for the spectral measure. Generalisation to trace class perturbations is also considered. The third algorithm is the infinite dimensional QL algorithm. In contrast to the finite dimensional case in which the QL and QR algorithms are equivalent, we find that the QL factorisations do not always exist, but that it is possible, at least in the case of pert-Toeplitz Jacobi operators, to implement shifts to generate rapid convergence of the top left entry to an eigenvalue. A fascinating novelty here is that the infinite dimensional matrices are computed in their entirety and stored in tailor made data structures. Lastly, the connection coefficients matrix and the orthogonal transformations computed in the QL iterations can be combined to transform these pert-Toeplitz Jacobi operators isospectrally to a canonical form. This allows us to implement a functional calculus for pert-Toeplitz Jacobi operators.
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Zabroda, Olga Nikolaievna. "Generalized convolution operators and asymptotic spectral theory." Doctoral thesis, Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200602061.
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The dissertation contributes to the further advancement of the theory of various classes of discrete and continuous (integral) convolution operators. The thesis is devoted to the study of sequences of matrices or operators which are built up in special ways from generalized discrete or continuous convolution operators. The generating functions depend on three variables and this leads to considerably more complicated approximation sequences. The aim was to obtain for each case a result analogous to the first Szegö limit theorem providing the first order asymptotic formula for the spectra of regular convolutions.
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Harutyunyan, Anahit V. "Toeplitz operators and division theorems in anisotropic spaces of holomorphic functions in the polydisc." Universität Potsdam, 2001. http://opus.kobv.de/ubp/volltexte/2008/2611/.
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This work is an introduction to anisotropic spaces, which have an ω-weight of analytic functions and are generalizations of Lipshitz classes in the polydisc. We prove that these classes form an algebra and are invariant with respect to monomial multiplication. These operators are bounded in these (Lipshitz and Djrbashian) spaces. As an application, we show a theorem about the division by good-inner functions in the mentioned classes is proved.
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Pang, Hong Kui. "New numerical methods and analysis for Toeplitz matrices with financial applications." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2492157.
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Randriamahaleo, Fanilo rajaofetra. "Opérateurs de Toeplitz sur l'espace de Bergman harmonique et opérateurs de Teoplitz tronqués de rang fini." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0108/document.
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Dans la première partie de la thèse, nous donnons les résultats classiques concernant l’espace de Hardy, les espaces modèles et les espaces de Bergman analytique et harmonique. Les notions de base telles que les projections et les noyaux reproduisant y sont introduites. Nous exposons ensuite nos résultats concernant d’une part, la stabilité du produit et la commutativité de deux opérateurs de Toeplitz quasihomogènes et d’autre part, la description matricielle des opérateurs de Toeplitz tronqués du type "a" "dans le cas de la dimension finieIn the first part of the thesis,we give some classical results concerning theHardy space, models spaces and analytic and harmonic Bergman spaces. The basic concepts such as projections and reproducing kernels are introduced. We then describe our results on the the stability of the product and the commutativity of two quasihomogeneous Toeplitz operators on the harmonic Bergman space. Finally, we give the matrix description of truncated Toeplitz operators of type "a" in the finite dimensional case
30
Falk, Kevin. "Berezin--Toeplitz quantization and noncommutative geometry." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4033/document.
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Cette thèse montre en quoi la quantification de Berezin--Toeplitz peut être incorporée dans le cadre de la géométrie non commutative.Tout d'abord, nous présentons les principales notions abordées : les opérateurs de Toeplitz (classiques et généralisés), les quantifications géométrique et par déformation, ainsi que quelques outils de la géométrie non commutative.La première étape de ces travaux a été de construire des triplets spectraux (A,H,D) utilisant des algèbres d'opérateurs de Toeplitz sur les espaces de Hardy et Bergman pondérés relatifs à des ouverts Omega de Cn à bord régulier et strictement pseudoconvexes, ainsi que sur l'espace de Fock sur Cn. Nous montrons que les espaces non commutatifs induits sont réguliers et possèdent la même dimension que le domaine complexe sous-jacent. Différents opérateurs D sont aussi présentés. Le premier est l'opérateur de Dirac usuel sur L2(Rn) ramené sur le domaine par transport unitaire, d'autres sont formés à partir de l'opérateur d'extension harmonique de Poisson ou de la dérivée normale complexe sur le bord de Omega.Dans un deuxième temps, nous présentons un triplet spectral naturel de dimension n+1 construit à partir du produit star de la quantification de Berezin--Toeplitz. Les éléments de l'algèbre correspondent à des suites d'opérateurs de Toeplitz dont chacun des termes agit sur un espace de Bergman pondéré. Plus généralement, nous posons des conditions pour lesquelles une somme infinie de triplets spectraux forme de nouveau un triplet spectral, et nous en donnons un exempleThe results of this thesis show links between the Berezin--Toeplitz quantization and noncommutative geometry.We first give an overview of the three different domains we handle: the theory of Toeplitz operators (classical and generalized), the geometric and deformation quantizations and the principal tools we use in noncommutative geometry.The first step of the study consists in giving examples of spectral triples (A,H,D) involving algebras of Toeplitz operators acting on the Hardy and weighted Bergman spaces over a smoothly bounded strictly pseudoconvex domain Omega of Cn, and also on the Fock space over Cn. It is shown that resulting noncommutative spaces are regular and of the same dimension as the complex domain. We also give and compare different classes of operator D, first by transporting the usual Dirac operator on L2(Rn) via unitaries, and then by considering the Poisson extension operator or the complex normal derivative on the boundary.Secondly, we show how the Berezin--Toeplitz star product over Omega naturally induces a spectral triple of dimension n+1 whose construction involves sequences of Toeplitz operators over weighted Bergman spaces. This result led us to study more generally to what extent a family of spectral triples can be integrated to form another spectral triple. We also provide an example of such triple
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Bauer, Wolfram [Verfasser]. "Toeplitz Operators on finite and infinite dimensional spaces with associated Psi*-Fréchet Algebras / Wolfram Bauer." Aachen : Shaker, 2006. http://d-nb.info/1186587393/34.
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Issa, Hassan A. [Verfasser], Wolfram [Akademischer Betreuer] Bauer, and Ingo [Akademischer Betreuer] Witt. "The analysis of Toeplitz operators, commutative Toeplitz algebras and applications to heat kernel constructions / Hassan A. Issa. Gutachter: Wolfram Bauer ; Ingo Witt. Betreuer: Wolfram Bauer." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1042970947/34.
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Bogveradze, Giorgi. "Fredholm theory for Wiener-Hopf plus Hankel operators." Doctoral thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/2935.
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Doutoramento em MatemáticaNa presente tese consideramos combinações algébricas de operadores de Wiener-Hopf e de Hankel com diferentes classes de símbolos de Fourier. Nomeadamente, foram considerados símbolos matriciais na classe de elementos quase periódicos, semi-quase periódicos, quase periódicos por troços e certas funções matriciais sectoriais. Adicionalmente, foi dedicada atenção também aos operadores de Toeplitz mais Hankel com símbolos quase periódicos por troços e com símbolos escalares possuindo n pontos de discontinuidades quase periódicas usuais. Em toda a tese, um objectivo principal teve a ver com a obtenção de descrições para propriedades de Fredholm para estas classes de operadores. De forma a deduzir a invertibilidade lateral ou bi-lateral para operadores de Wiener-Hopf mais Hankel com símbolos matriciais AP foi introduzida a noção de factorização assimétrica AP. Neste âmbito, foram dadas condições suficientes para a invertibilidade lateral e bi-lateral de operadores de Wiener- Hopf mais Hankel com símbolos matriciais AP. Para tais operadores, foram ainda exibidos inversos generalizados para todos os casos possíveis. Para os operadores de Wiener-Hopf-Hankel com símbolos matriciais SAP e PAP foi deduzida a propriedade de Fredholm e uma fórmula para a soma dos índices de Fredholm destes operadores de Wiener-Hopf mais Hankel e operadores de Wiener-Hopf menos Hankel. Uma versão mais forte destes resultados foi obtida usando a factorização generalizada AP à direita. Foram analisados os operadores de Wiener-Hopf-Hankel com símbolos que apresentam determinadas propriedades pares e também com símbolos de Fourier que contêm matrizes sectoriais. Em adição, para operadores de Wiener-Hopf-Hankel, foi obtido um resultado correspondente ao teorema clássico de Douglas e Sarason conhecido para operadores de Toeplitz com símbolos sectoriais e unitários. Condições necessárias e suficientes foram também deduzidas para que os operadores de Wiener-Hopf mais Hankel com símbolos L∞ sejam de Fredholm (ou invertíveis). Para se obter tal resultado, trabalhou-se com certas factorizações ímpares dos símbolos de Fourier. Os operadores de Toeplitz mais Hankel gerados por símbolos que possuem n pontos de discontinuidades quase periódicas usuais foram também considerados. Foram obtidas condições sob as quais estes operadores são invertíveis à direita e com dimensão de núcleo infinita, invertíveis à esquerda e com dimensão de co-núcleo infinita ou não normalmente solúveis. A nossa atenção foi também colocada em operadores de Toeplitz mais Hankel com símbolos matriciais contínuos por troços. Para tais operadores, condições necessárias e suficientes foram obtidas para se ter a propriedade de Fredholm. Tal foi realizado usando a abordagem do cálculo simbólico, determinados operadores auxiliares emparelhados com símbolos semi-quase periódicos e várias relações de equivalência após extensão entre operadores.
In this thesis we considered algebraic combinations of Wiener-Hopf and Hankel operators with different classes of Fourier symbols. Namely, matrix symbols from the almost periodic, semi-almost periodic, piecewise almost periodic and certain sectorial matrix functions were considered. In addition, attention was also paid to Toeplitz plus Hankel operators with piecewise almost periodic symbols and with scalar symbols having n points of standard almost periodic discontinuities. In the entire thesis a main goal is to obtain Fredholm properties description of those classes of operators. To deduce the lateral or both sided invertibility theory for Wiener-Hopf plus Hankel operators with AP matrix symbols was introduced the notion of an AP asymmetric factorization. In this framework were given sufficient conditions for the lateral and both sided invertibility of the Wiener-Hopf plus Hankel operators with matrix AP symbols. For such kind of operators were also exhibited generalized inverses for all the possible cases. For the Wiener-Hopf-Hankel operators with matrix SAP and PAP symbols the Fredholm property and a formula for the sum of the Fredholm indices of these Wiener-Hopf plus Hankel and Wiener-Hopf minus Hankel operators were derived. A stronger version of these results was obtained by using the generalized right AP factorization. It was analyzed the Wiener-Hopf-Hankel operators with symbols presenting some even properties, and also with Fourier symbols which contain sectorial matrices. In addition, for Wiener-Hopf-Hankel operators, it was obtained a corresponding result to the classical theorem by Douglas and Sarason known for Toeplitz operators with sectorial and unitary valued symbols. Necessary and sufficient condition for the Wiener-Hopf plus Hankel operators with L∞ symbols to be Fredholm (or invertible) were also derived. To obtain such a result we dealt with certain odd asymmetric factorization of the Fourier symbols. The Toeplitz plus Hankel operators generated by symbols which have n points of standard almost periodic discontinuities were also considered. Conditions were obtained under which these operators are right-invertible and with infinite kernel dimension, left-invertible and with infinite cokernel dimension or simply not normally solvable. We also focused our attention to Toeplitz plus Hankel operators with piecewise almost periodic matrix symbols. For such operators necessary and sufficient conditions were obtained to have the Fredholm property. This was done using a symbol calculus approach, certain auxiliary paired operators with semi-almost periodic symbols, and several equivalence after extension operator relations.
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Rouby, Ophélie. "Conditions de quantification de Bohr-Sommerfeld pour des opérateurs semi-classiques non auto-adjoints." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S051/document.
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On s'intéresse à la théorie spectrale d'opérateurs semi-classiques non auto-adjoints en dimension un et plus précisément aux développements asymptotiques des valeurs propres. Ces derniers font intervenir des objets géométriques issus de la mécanique classique dans l'espace des phases complexifié et correspondent à une généralisation des conditions de quantification de Bohr-Sommerfeld au cadre non auto-adjoint. Plus précisément, dans un premier temps, on étudie le spectre de perturbations non auto-adjointes d'opérateurs pseudo-différentiels auto-adjoints en dimension un à l'aide de techniques d'analyse microlocale analytique et en corollaire, on établit que pour des perturbations PT-symétriques d'opérateurs auto-adjoints, le spectre est réel. Ensuite, on présente des conditions de quantification de Bohr-Sommerfeld pour des perturbations non auto-adjointes d'opérateurs de Berezin-Toeplitz du plan complexe auto-adjoints. Dans un second temps, on s'intéresse aux différentes quantifications du tore et plus précisément à la quantification de Berezin-Toeplitz du tore, à la quantification de Weyl classique du tore et à la quantification de Weyl complexe du tore. On établit des liens entre ces différentes quantifications notamment grâce à la transformée de Bargmann, puis à l'aide de simulations numériques, on met en évidence une conjecture sur des conditions de quantification de Bohr-Sommerfeld pour des perturbations non auto-adjointes d'opérateurs de Berezin-Toeplitz du tore auto-adjointsWe interest ourselves in the spectral theory of non self-adjoint semi-classical operators in dimension one and in asymptotic expansions of eigenvalues. These expansions are written in terms of geometrical objects in a complex phase space coming from classical mechanics and correspond to a generalization of Bohr-Sommerfeld quantization conditions in the non self-adjoint case. First, we study non self-adjoint perturbations of self-adjoint pseudo-differential operators in dimension one by using techniques of analytic microlocal analysis. As a corollary, we establish for PT-symmetric perturbations of self-adjoint operators, that the spectrum is real. Then we show Bohr-Sommerfeld quantization conditions for non self-adjoint perturbations of self-adjoint Berezin-Toeplitz operators of the complex plane. In the second part, we look into quantizations of the torus, namely the Berezin-Toeplitz, the classical Weyl and the complex Weyl quantizations of the torus. We establish links between these different quantizations using Bargmann transform. We propose a conjecture, supported by numerical simulations, on Bohr-Sommerfeld quantization conditions for non self-adjoint perturbations of self-adjoint Berezin-Toeplitz operators of the torus
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Zhang, Ying Ying. "Preconditioning techniques for a family of Toeplitz-like systems with financial applications." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2151602.
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Tytgat, Romaric. "Trace de Dixmier d'opérateurs de Hankel." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4772/document.
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Nous nous intéressons aux opérateurs de Hankel $H_{bar{f}}$ de symbole anti holomorphe $bar{f}$ et regardons l'espace de Dixmier $mathcal{D}^{p}$ associé ($pgeq1$), c'est à dire l'ensemble des $f$ tel que $|H_{bar{f}}|^{p}$ soit dans l'idéal de Macaev $mathcal{S}^{+}_{1}$. Notre approche est de voir l'espace de Dixmier comme une certaine limite des classes de Schatten. Quand $f in mathcal{D}^{p}$, nous étudions $Tr_{omega}(|$H_{bar{f}}$|^{p})$ la trace de Dixmier de $|H_{bar{f}}|^{p}$. Nous redémontrons certains résultats classiques quand $f$ est holomorphe sur le disque alors que nous donnons de nouveaux résultats quand $f$ est entière. Nous utilisons notre méthode pour étudier l'espace de Dixmier du petit opérateur de Hankel, des opérateurs de Toeplitz $T_{varphi}$ ($varphi$ définie sur le disque ou sur le plan complexe tout entier) ainsi que pour l'opérateur de compositionWe study Hankel operators $H_{bar{f}}$ with anti holomorphic symbol $bar{f}$ and we are interested to the Dixmier space $mathcal{D}^{p}$ ($pgeq1$), the set of functions $f$ such that $|H_{bar{f}}|^{p} in mathcal{S}^{+}_{1}$ the Macaev ideal. We look Dixmier space as a limit of Schatten class. When $f in mathcal{D}^{p}$, we study $Tr_{omega}(|$H_{bar{f}}$|^{p})$ the Dixmier trace of $|H_{bar{f}}|^{p}$. We have different results when $f$ is an entire or a holomorphic function of the unit disk in the complex plan. We study also the Dixmier space of the little Hankel operator, Toeplitz operator and composition operator
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Detcherry, Renaud. "Analyse semi-classique des opérateurs courbes en TQFT." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066252/document.
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Witten, Reshetikhin et Turaev ont défini des invariants des variétés topologiques de dimension 3, dits "quantiques" qui s'étendent en une structure de TQFT, c'est-à-dire un foncteur monoïdal d'une catégorie de cobordismes vers la catégorie des espaces vectoriels complexes. Nous étudions ici leur asymptotique. Dans ce cadre, les courbes sur une surface induisent des endomorphismes des espaces de TQFT, appelés opérateurs courbes, qui sont l'un des objets centraux du mémoire. Tous ces invariants dépendant d'un paramètre entier r, on s'intéresse à leur comportement quand r tend vers l'infini. On s'aperçoit alors que les invariants quantiques sont liés à des objets plus géométriques, comme les espaces des modules des représentations dans SU2 du groupe fondamental d'une surface. La première partie de la thèse introduit la notion de TQFT et les invariants de Witten-Reshetikhin-Turaev, puis donne des rudiments de géométrie de l'espace des modules SU2 d'une surface et de quantification géométrique. La deuxième partie présente un résultat sur l'asymptotique des coefficients de matrices des opérateurs courbes en TQFT. A partir de calcul d'écheveau et d'un théorème de Bullock, on relie les deux premiers termes de leur développement aux fonctions traces associées aux multicourbes. Cette thèse aboutit dans la troisième partie à un résultat asymptotique pour les coefficients de matrices des représentations quantiques. Un modèle géométrique est proposé pour les espaces de TQFT associés aux surfaces, et il est montré que les opérateurs courbes s'identifient alors à des opérateurs de Toeplitz. Des méthodes standards d'analyse semi-classiques permettent d'en déduire le résultatIn this thesis we study the asymptotics of some invariants of 3-manifolds, known as "quantum invariants" which were defined by Witten, Reshetikhin and Turaev. These invariants are part of a TQFT structure, that is a monoidal functor for a category of cobordism to the category of complex vector spaces. In this setting, curves on surfaces induce endomorphisms of TQFT vector spaces, called curve operators, which are one of the main object in our study. All these invariants depend of an integer parameter r, and we are interested in their behavior when r tends to infinity. We can then see that quantum invariants are related to more geometric objects, like the moduli space of conjugacy classes of SU2 representations of the fundamental group of a surface. The thesis is divided in 3 parts: in the first one we introduce the notion of TQFT and the Witten-Reshetikhin-Turaev invariants, then we give basic properties of the SU2-moduli spaces and explain the general approach of geometric quantification. In the second one we present a result on the asymptotics of matrix coefficients of curve operators. Using skein calculus and a theorem of Bullock, we express the first two terms of their expansion in terms of trace functions on the SU2-moduli space associated to multicurves. The final part gives an asymptotic expansion of matrix coefficents of quantum representations. A geometric model for TQFT vector spaces is defined, and we show that curve operators can be seen as Toeplitz operators in this model. Standard tools of semi-classical analysis allow us to deduce the result from this
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Le, Floch Yohann. "Théorie spectrale inverse pour les opérateurs de Toeplitz 1D." Phd thesis, Université Rennes 1, 2014. http://tel.archives-ouvertes.fr/tel-01065441.
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Dans cette thèse, nous prouvons des résultats de théorie spectrale, directe et inverse, dans la limite semi-classique, pour les opérateurs de Toeplitz autoadjoints sur les surfaces. Pour les opérateurs pseudo-différentiels, les résultats en question sont déjà connus, et il est naturel de vouloir les étendre aux opérateurs de Toeplitz. Les conditions de Bohr-Sommerfeld usuelles, qui caractérisent les valeurs propres proches d'une valeur régulière du symbole principal, ont été obtenues il y a quelques années seulement pour les opérateurs de Toeplitz. Notre contribution consiste en l'extension de ces conditions près de valeurs critiques non dégénérées. Nous traitons le cas d'une valeur critique elliptique à l'aide d'une technique de forme normale ; l'opérateur modèle est la réalisation de l'oscillateur harmonique sur l'espace de Bargmann, dont le spectre est bien connu. Dans le cas d'une valeur critique hyperbolique, la forme normale ne suffit plus et nous complétons l'étude en faisant appel à des arguments dus à Colin de Verdière et Parisse, à qui l'on doit le résultat analogue dans le cas pseudo-différentiel. Enfin, nous établissons un résultat de théorie spectrale inverse pour les opérateurs de Toeplitz autoadjoints sur les surfaces ; plus précisément, nous montrons que sous certaines hypothèses génériques, la connaissance du spectre à l'ordre deux dans la limite semi-classique permet de retrouver le symbole principal à symplectomorphisme près. Ce résultat s'appuie en grande partie sur l'écriture des règles de Bohr-Sommerfeld.
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Arroussi, Hicham. "Function and Operator Theory on Large Bergman spaces." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/395175.
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The theory of Bergman spaces has been a central subject of study in complex analysis during the past decades. The book [7] by S. Bergman contains the first systematic treat-ment of the Hilbert space of square integrable analytic functions with respect to Lebesgue area measure on a domain. His approach was based on a reproducing kernel that became known as the Bergman kernel function. When attention was later directed to the spaces AP over the unit disk, it was natural to call them Bergman spaces. As counterparts of Hardy spaces, they presented analogous problems. However, although many problems in Hardy spaces were well understood by the 1970s, their counterparts for Bergman spaces were generally viewed as intractable, and only some isolated progress was done. The 1980s saw the emerging of operator theoretic studies related to Bergman spaces with important contributions by several authors. Their achievements on Bergman spaces with standard weights are presented in Zhu's book [77]. The main breakthroughs came in the 1990s, where in a flurry of important advances, problems previously considered intractable began to be solved. First came Hedenmalm's construction of canonical divisors [26], then Seip's description [59] of sampling and interpolating sequences on Bergman spaces, and later on, the study of Aleman, Richter and Sundberg [1] on the invariant subspaces of A2, among others. This attracted other workers to the field and inspired a period of intense research on Bergman spaces and related topics. Nowadays there are rich theories on Bergman spaces that can be found on the textbooks [27] and [22].
Meanwhile, also in the nineties, some isolated problems on Bergman spaces with ex-ponential type weights began to be studied. These spaces are large in the sense that they contain all the Bergman spaces with standard weights, and their study presented new dif-ficulties, as the techniques and ideas that led to success when working on the analogous problems for standard Bergman spaces, failed to work on that context. It is the main goal of this work to do a deep study of the function theoretic properties of such spaces, as well as of some operators acting on them. It turns out that large Bergman spaces are close in spirit to Fock spaces [79], and many times mixing classical techniques from both Bergman and Fock spaces in an appropriate way, can led to some success when studying large Bergman spaces.
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Gioev, Dimitri. "Generalizations of Szego Limit Theorem : Higher Order Terms and Discontinuous Symbols." Doctoral thesis, KTH, Mathematics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3123.
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Casseli, Irène. "Eléments sur la transformée de Berezin et sur les opérateurs de Toeplitz dans des espaces de fonctions polyanalytiques." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0578.
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Les fonctions polyanalytiques entières généralisent les fonctions entières dans la mesure où elles sont les solutions sur le plan complexe \mathbb{C} de l'équation de Cauchy-Riemann à l'ordre n, de la forme { partial} nf / \partial \overline{z} n = 0. Un espace de Fock polyanalytique F2 {\alpha,n} est, par analogie avec le cas classique, le sous-espace fermé de l'espace de Hilbert L^2 (\mathbb{C},d\mu \alpha), où \mu \alpha est une mesure de probabilité gaussienne sur \mathbb{C} de paramètre alpha>0, formé des fonctions polyanalytiques entières d'ordre n. L'objet de cette thèses est l'étude d'éléments classiques de la théorie des opérateurs tels que la transformée de Berezin et les opérateurs de Toeplitz dans le cadre particulier des espaces de Fock polyanalytiques. Dans ce manuscrit, il est montré en particulier que les points fixes de la transformée de Berezin qui appartiennent aux espaces de Lebesgue sont les fonctions nulles ou éventuellement constantes. Concernant les opérateurs de Toeplitz, le problème de Sarason est étudié. Etant donné une fonction f, l'opérateur de Toeplitz de symbole f est formellement défini par T {alpha,n} f(h)=P {alpha,n}(f h), où P {alpha,n} est la projection orthogonale de L^2(\mathbb{C},d\mu {alpha}) sur F^2 {alpha,n}. Le problème de Sarason consiste à donner une condition nécessaire et suffisante sur f et g pour que le produit d'opérateurs de symboles f et bar g soit continuEntire polyanalytic functions generalize entire functions in that they are solutions of "Cauchy-Riemann equations of order n, of the form {\partial}^n f / \partial \overline{z}^n = 0, over the whole complex plane \mathbb{C}. Polyanalytic Fock space F^2_{\alpha,n} is, by analogy with the classical case, the closed subspace of the Hilbert space L^2(\mathbb{C},d\mu_\alpha), where \mu_\alpha is a Gaussian probability measure over \mathbb{C} with weight \alpha>0, of polyentire functions of order n. The aim of this PhD thesis is the study of classical objects of operator theory such that the Berezin transform and Toeplitz operators in the particular case of polyanalytic Fock spaces. In this written, it is shown among other results, that the L^p fixed points of the Berezin transform are constant functions. Concerning Toeplitz operators, the Sarason problem is studied. Given a function f, the Toeplitz operator with symbol f is formally defined by T^n_f(h)=P_{F^2_n}(f h), where P_{F^2_n} is the orthogonal projection from L^2(\mathbb{C},d\mu) on to F^2_n. The so-called Sarason's problem consists in finding necessary and sufficient conditions on the symbols f and g for the Toeplitz product with symbols f and \bar g to be bounded in the Fock space
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Langendörfer, Sebastian [Verfasser], and Jörg [Akademischer Betreuer] Eschmeier. "On unitarily invariant subspaces and Cowen-Douglas theory : characterization of Toeplitz operators, Wold decomposition type theorems and fiber dimension for invariant subspaces / Sebastian Langendörfer ; Betreuer: Jörg Eschmeier." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2019. http://d-nb.info/1196090149/34.
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Langendörfer, Sebastian Verfasser], and Jörg [Akademischer Betreuer] [Eschmeier. "On unitarily invariant subspaces and Cowen-Douglas theory : characterization of Toeplitz operators, Wold decomposition type theorems and fiber dimension for invariant subspaces / Sebastian Langendörfer ; Betreuer: Jörg Eschmeier." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2019. http://nbn-resolving.de/urn:nbn:de:bsz:291--ds-287558.
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Le, Van An. "Petits espaces de Fock, petits espaces de Bergman et leurs opérateurs." Thesis, Aix-Marseille, 2019. http://theses.univ-amu.fr.lama.univ-amu.fr/191210_LE_604try554eejyoj865ovdfq987fxy_TH.pdf.
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Nous étudions les mesures de Carleson et les opérateurs de Toeplitz sur la classe des espaces de Bergman dite de petite taille, introduits récemment par Seip. On obtient une caractérisation des mesures de Carleson qui étend les résultats de Seip à partir du disque unité de mathbb C à la boule unité mathbb Bn de mathbb Cn. Nous utilisons cette caractérisation pour donner les conditions nécessaires et suffisantes à la continuité et à la compacité des opérateurs de Toeplitz. Enfin, nous étudions l’appartenance des opérateurs Toeplitz aux classes de Schatten d'ordre p pour 1We study the Carleson measures and the Toeplitz operators on the class of the so-called small weighted Bergman spaces, introduced recently by Seip. A characterization of Carleson measures is obtained which extends Seip's results from the unit disk of mathbb C to the unit ball mathbb Bn of mathbb Cn. We use this characterization to give necessary and sufficient conditions for the boundedness and compactness of Toeplitz operators. Finally, we study the Schatten p classes membership of Toeplitz operators for 1
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Meyer, Julien. "Quantisation of the Laplacian and a Curved Version of Geometric Quantisation." Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/235181.
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Let (E,h) be a holomorphic, Hermitian vector bundle over a polarized manifold. We provide a canonical quantisation of the Laplacian operator acting on sections of the bundle of Hermitian endomorphisms of E. If E is simple we obtain an approximation of the eigenvalues and eigenspaces of the Laplacian. In the case when the bundle E is the trivial line bundle, we quantise solutions to the heat equation on the manifold. Furthermore we show that geometric quantisation can be seen as the differential of a natural map between two Riemannian manifolds. Motivated by this fact we compute its next order approximation, namely its Hessian.Option Mathématique du Doctorat en Sciences
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BOUAZIZ, MALEK. "Operateurs de toeplitz et applications statistiques." Paris 11, 1994. http://www.theses.fr/1994PA112057.
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Ce travail est motive par des problemes de statistique asymptotique de suites de modeles gaussiens stationnaires, et par leur relation avec la theorie des operateurs de toeplitz. Le modele d'ordre n est specifie par un parametre, densite spectrale sur le cercle unite, et une probabilite gaussienne, de dimension n, centree et de covariance egale a la matrice de toeplitz d'ordre n associee a ce parametre. Nous construisons des classes de parametres dans des algebres de krein, des operateurs de toeplitz associes a ces parametres et inversibles, et des formules d'inversion asymptotique de ces operateurs. Nous calculons aussi une borne superieure pour la norme nucleaire de l'ecart entre un produit fini de matrices de toeplitz associees a des parametres donnes et la matrice de toeplitz associee au produit de ces parametres. Nous montrons ensuite comment ces resultats permettent de construire des approximations pour des rapports vraisemblance adaptees a des problemes de tests d'hypotheses et d'estimation. Nous precisons aussi le role du periodogramme dans ces problemes, et nous etablissons un developpement asymptotique pour ces rapports (propriete lan en dimension infinie). D'autres applications concernent le periodogramme: comportement de ces cumulants, inegalites de type berry-esseen, loi du logarithme itere. Enfin, nous considerons le cas de parametres rationnels (modeles arma). Utilisant des vraisemblances exactes ou approchees, et la loi du logarithme itere, nous construisons des estimateurs consistants pour les degres (ordre) du parametre
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Langenau, Holger. "Best constants in Markov-type inequalities with mixed weights." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-200815.
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Markov-type inequalities provide upper bounds on the norm of the (higher order) derivative of an algebraic polynomial in terms of the norm of the polynomial itself. The present thesis considers the cases in which the norms are of the Laguerre, Gegenbauer, or Hermite type, with respective weights chosen differently on both sides of the inequality. An answer is given to the question on the best constant so that such an inequality is valid for every polynomial of degree at most n. The demanded best constant turns out to be the operator norm of the differential operator. The latter conicides with the tractable spectral norm of its matrix representation in an appropriate set of orthonormal bases. The methods to determine these norms vary tremendously, depending on the difference of the parameters accompanying the weights. Up to a very small gap in the parameter range, asymptotics for the best constant in each of the aforementioned cases are givenMarkovungleichungen liefern obere Schranken an die Norm einer (höheren) Ableitung eines algebraischen Polynoms in Bezug auf die Norm des Polynoms selbst. Diese vorliegende Arbeit betrachtet den Fall, dass die Normen vom Laguerre-, Gegenbauer- oder Hermitetyp sind, wobei die entsprechenden Gewichte auf beiden Seiten unterschiedlich gewählt werden. Es wird die kleinste Konstante bestimmt, sodass diese Ungleichung für jedes Polynom vom Grad höchstens n erfüllt ist. Die gesuchte kleinste Konstante kann als die Operatornorm des Differentialoperators dargestellt werden. Diese fällt aber mit der Spektralnorm der Matrixdarstellung in einem Paar geeignet gewählter Orthonormalbasen zusammen und kann daher gut behandelt werden. Zur Abschätzung dieser Normen kommen verschiedene Methoden zum Einsatz, die durch die Differenz der in den Gewichten auftretenden Parameter bestimmt werden. Bis auch eine kleine Lücke im Parameterbereich wird das asymptotische Verhalten der kleinsten Konstanten in jedem der betrachteten Fälle ermittelt
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Vasil'ev, Vladimir A. Silbermann Bernd. "Second-order trace formulas in Szegö-type theorems." [S.l. : s.n.], 2007.
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Seidel, Markus Silbermann Bernd. "Über die Splitting-Eigenschaft der Approximationszahlen von Matrix-Folgen : l1-Theorie$nElektronische Ressource /." [S.l. : s.n.], 2006.
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Langenau, Holger. "Best constants in Markov-type inequalities with mixed weights." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2015. https://monarch.qucosa.de/id/qucosa%3A20429.
Full textAbstract:
Markov-type inequalities provide upper bounds on the norm of the (higher order) derivative of an algebraic polynomial in terms of the norm of the polynomial itself. The present thesis considers the cases in which the norms are of the Laguerre, Gegenbauer, or Hermite type, with respective weights chosen differently on both sides of the inequality. An answer is given to the question on the best constant so that such an inequality is valid for every polynomial of degree at most n.
The demanded best constant turns out to be the operator norm of the differential operator. The latter conicides with the tractable spectral norm of its matrix representation in an appropriate set of orthonormal bases.
The methods to determine these norms vary tremendously, depending on the difference of the parameters accompanying the weights. Up to a very small gap in the parameter range, asymptotics for the best constant in each of the aforementioned cases are given.Markovungleichungen liefern obere Schranken an die Norm einer (höheren) Ableitung eines algebraischen Polynoms in Bezug auf die Norm des Polynoms selbst. Diese vorliegende Arbeit betrachtet den Fall, dass die Normen vom Laguerre-, Gegenbauer- oder Hermitetyp sind, wobei die entsprechenden Gewichte auf beiden Seiten unterschiedlich gewählt werden. Es wird die kleinste Konstante bestimmt, sodass diese Ungleichung für jedes Polynom vom Grad höchstens n erfüllt ist. Die gesuchte kleinste Konstante kann als die Operatornorm des Differentialoperators dargestellt werden. Diese fällt aber mit der Spektralnorm der Matrixdarstellung in einem Paar geeignet gewählter Orthonormalbasen zusammen und kann daher gut behandelt werden. Zur Abschätzung dieser Normen kommen verschiedene Methoden zum Einsatz, die durch die Differenz der in den Gewichten auftretenden Parameter bestimmt werden. Bis auch eine kleine Lücke im Parameterbereich wird das asymptotische Verhalten der kleinsten Konstanten in jedem der betrachteten Fälle ermittelt.