Dissertations / Theses on the topic 'Complex analytical functions'

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In this work we describe soem properties of the complex numbers and analytical functions. As an application, we use the conformal transformations to caculate analytical solutions for electromagnetic problems defined in nonconventional domain. The conformal transformation are of excepcional importance in solving boundary value problems in electromagnetic theory. The conformal transformation have the property of modifying the geometry, but preserving the pysical quantities.
Neste trabalho descrevemos algumas propriedades dos números complexos e das funções analíticas complexas. Como aplicação, usamos as transformações conformes para calcular de forma analítica a solução de problemas eletromagnéticos definidos em domínios não convencionais. As transformações conformes são de excepcional importância na resolução de problemas de valores de contorno na teoria eletromagnética. As transformações conformes têm a propriedade de modificar a geometria, preservando as grandezas físicas.

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O objetivo principal deste trabalho é desenvolver um estudo introdutório, porém detalhado, sobre Análise Complexa e algumas de suas aplicações. Apresentamos o corpo dos números complexos, exploramos as funções complexas de uma variável complexa, exibimos parte da teoria das funções analíticas e parte da teoria de integração complexa. Provamos importantes resultados, tais como o Teorema de Cauchy, o Teorema de Taylor, o Teorema dos Resíduos, entre outros igualmente relevantes. Como aplicação da teoria, destacamos a utilização do Teorema dos Resíduos para determinar a transformada inversa de Laplace de uma função F(s).
The main objective of this work is to develop an introductory but detailed study on Complex Analysis and some of its applications. We present the field of the complex numbers, explore the complex functions of a complex variable, exhibit part of the theory of analytic functions, and part of the complex integration theory. We prove important results, such as Cauchy’s Theorem, Taylor’s Theorem, Residue Theorem, among others equally relevant. As an application of the theory, we highlight the use of the Residue Theorem to determine the inverse Laplace transform of a function F(s).

In this thesis we present certain spaces of analytic functions on the complex half-plane, including the Hardy, the Bergman spaces, and their generalisation: Zen spaces. We use the latter to construct a new type of spaces, which include the Dirichlet and the Hardy-Sobolev spaces. We show that the Laplace transform defines an isometric map from the weighted L^2(0, ∞) spaces into these newly-constructed spaces. These spaces are reproducing kernel Hilbert spaces, and we employ their reproducing kernels to investigate their features. We compare corresponding spaces on the disk and on the half-plane. We present the notions of Carleson embeddings and Carleson measures and characterise them for the spaces introduced earlier, using the reproducing kernels, Carleson squares and Whitney decomposition of the half-plane into an abstract tree. We also study multiplication operators for these spaces. We show how the Carleson measures can be used to test the boundedness of these operators. We show that if a Hilbert space of complex valued functions is also a Banach algebra with respect to the pointwise multiplication, then it must be a reproducing kernel Hilbert space and its kernels are uniformly bounded. We provide examples of such spaces. We examine spectra and character spaces corresponding to multiplication operators. We study weighted composition operators and, using the concept of causality, we link the boundedness of such operators on Zen spaces to Bergman kernels and weighted Bergman spaces. We use this to show that a composition operator on a Zen space is bounded only if it has a finite angular derivative at infinity. We also prove that no such operator can be compact. We present an application of spaces of analytic functions on the half-plane in the study of linear evolution equations, linking the admissibility criterion for control and observation operators to the boundedness of Laplace-Carleson embeddings.

This thesis is concerned with a conjecture of Zilber: that the complex field expanded with the exponential function should be `quasi-minimal'; that is, all its definable subsets should be countable or have countable complement. Our purpose is to study the geometry of this structure and other expansions by holomorphic functions of the complex field without having first to settle any number-theoretic problems, by treating all countable sets on an equal footing. We present axioms, modelled on those for a Zariski geometry, defining a non-first-order class of ``quasi-Zariski'' structures endowed with a dimension theory and a topology in which all countable sets are of dimension zero. We derive a quantifier elimination theorem, implying that members of the class are quasi-minimal. We look for analytic structures in this class. To an expansion of the complex field by entire holomorphic functions $\mathcal{R}$ we associate a sheaf $\mathcal{O}^{\scriptscriptstyle{\mathcal{R}}}$ of analytic germs which is closed under application of the implicit function theorem. We prove that $\mathcal{O}^{\scriptscriptstyle{\mathcal{R}}}$ is also closed under partial differentiation and that it admits Weierstrass preparation. The sheaf defines a subclass of the analytic sets which we call $\mathcal{R}$-analytic. We develop analytic geometry for this class proving a Nullstellensatz and other classical properties. We isolate a condition on the asymptotes of the varieties of certain functions in $\mathcal{R}$. If this condition is satisfied then the $\mathcal{R}$-analytic sets induce a quasi-Zariski structure under countable union. In the motivating case of the complex exponential we prove a low-dimensional case of the condition, towards the original conjecture.

Esta dissertação trata do Princípio da similaridade para as soluções das equações da forma L\'OMEGA\' = A(z) ·\'OMEGA\' + B(z) · \'BARRA\' \'omega\' , sendo L um campo vetorial complexo não singular e A,B \'PERTENCE\' \'C POT. sigma\' (\'R POT. 2\'), com 0 < \'sigma\' < 1. Aqui são apresentados resultados para o campo vetorial elítico L = \'PARTIAL SUP\' \'\'PARTIAL\' z e para classes de campos vetoriais elíticos degenerados
This dissertation deals with the Similarity principle for solutions of equations of the form L \'omega\' = A(z) · \'omega\' + B(z) · \' BARRA\' \'omega\' where L is a nonsingular complex vector field and A,B \'IT BELONGS\' \'C POT. sigma \' (\'R POT. 2\'), with 0 < \'sigma\' < 1. Here are presented results for elliptic vector field and for classes of degenerate elliptic vector fields

Cette thèse est consacrée à l'étude de la régularité analytique globale de l'équation de Cauchy-Riemann sur des domaines bornés pseudoconvexes et réguliers dont le bord est analytique réel. Dans la première partie, nous obtenons, sous certaines conditions supplémentaires sur le domaine, la régularité analytique globale de la solution canonique de l'équation de Cauchy-Riemann sur le bord du domaine. Dans la deuxième partie, on obtient le résultat pour une classe de domaines pseudoconvexes en dimension complexe n.

In this paper we show how to give an intrinsic definition of a constructible circle on the sphere. The classical definition of constructible circle in the plane, using straight edge and compass is there by translated in ters of so called Lenart tools. The process by which we achieve our goal involves concepts from the algebra of Hermitian matrices, complex variables, and Sterographic projection. However, the discussion is entirely elementary throughout and hopefully can serve as a guide for teachers in advanced geometry.

Cette thèse est consacrée à la description de l'espace atteignable de l'équation de la chaleur à l'aide de méthodes de l'analyse complexe moderne. Ce problème central de la théorie du contrôle est vieux de 50 ans et a captivé de nombreuses recherches depuis les travaux pionniers de Fattorini et Russel en 1971. Dans ce travail, on s'intéresse à l'équation de la chaleur 1-D sur un segment avec contrôle de Dirichlet au bord.Dans une première partie, on démontre à l'aide d'un théorème de type Paley-Wiener que l'espace atteignable est égal à la somme de deux espaces de Bergman, puis qu'il contient un espace de Smirnov-Zygmund en étudiant la régularité de la transformée de Cauchy.Dans une deuxième partie, en utilisant des méthodes de noyaux reproduisants et de d-bar, on résout le problème de séparation de singularités (problème de type Cousin) pour l'espace de Bergman dans plusieurs configurations. On en déduit ainsi une caractérisation définitive de l'espace atteignable comme espace de Bergman sur un carré.Enfin, la dernière partie est consacrée à l'équation de chaleur avec un potentiel quadratique et à son espace atteignable
This thesis is devoted to the description of the reachable space of the heat equation using methods of modern complex analysis. This central problem in control theory is about 50 years old and has captivated a lot of research efforts since the pioneering work of Fattorini and Russell in 1971. In this work, we are interested in the 1-D heat equation on a segment with Dirichlet boundary control.In the first part, using a Paley-Wiener theorem we prove that the reachable space is the sum of two Bergman spaces, then that it contains a Smirnov-Zygmund space by studying the regularity of the Cauchy transform.In a second part, using reproducing kernels and d-bar methods, we solve the problem of separation of singularities (Cousin-type problem) for the Bergman space in several configurations. This enables us to deduce a definitive characterization of the reachable space as the Bergman space on a square.Finally, the last part is devoted to the heat equation with a quadratic potential and its reachable space

L’objectif de ce travail est d’améliorer la caractérisation des sources à l’origine d’anomalies magnétiques, par le biais de développements théoriques et expérimentaux. Pour des structures invariantes dans une direction horizontale (structures à 2D), l’idée de Nabighian (1972) a été généralisée, ce qui implique une nouvelle façon d’étudier les méthodes potentielles à 2D. Ces développements ont permis de proposer une nouvelle approche théorique et de nouvelles représentations dans le plan complexe des fonctions magnétiques. La deuxième approche de ce travail est expérimentale. Une étude y est faite par le biais de données et de cas synthétiques, afin d’estimer l’apport d’acquisitions magnétiques à différentes altitudes pour caractériser une source. Dans un troisième temps, les développements théoriques et expérimentaux sont mis en œuvre pour deux exemples : des anomalies magnétiques en domaine océanique de type Vine et Mathews et une cartographie pour l’archéologie
Magnetic anomalies recorded outside bodies provide high quality information relative to buried structures. By using theoretical and experimental developments, this thesis aims to improve the characterization of the source inducing the magnetic anomaly. Firstly, some properties of three dimensional magnetic functions are presented, for example the presence of several maxima of the analytic signal operator (3D) is demonstrated. The Nabighian (1972) equation is generalized, which imply a new process to study potential method in two dimensions. These developments enable a new visualization of the anomaly in the complex field. The second approach is experimental. Synthetic cases are used to estimate the contribution of different configurations of magnetic data acquisitions at different altitudes to characterize the magnetic source. Theoretical and experimental developments are finally applied to two field examples: oceanic magnetic anomalies and archaeological magnetic prospection

We wish to study those domains in Cn,for n ≥ 2, the so-called domains of holomorphy, which are in some sense the maximal domains of existence of the holomorphic functions defined on them. We demonstrate that this study is radically different from that of domains in C by discussing some examples of special types of domains in Cn , n ≥2, such that every function holomorphic on them extends to strictly larger domains. Given a domain in Cn , n ≥ 2, we wish to construct the maximal domain of existence for the holomorphic functions defined on the given domain. This leads to Thullen’s construction of a domain (not necessarily in Cn)spread overCn, the so-called envelope of holomorphy, which fulfills our criteria. Unfortunately this turns out to beavery abstract space, far from giving us sense in general howa domain sitting in Cn can be constructed which is strictly larger than the given domain and such that all the holomorphic functions defined on the given domain extend to it. But with the help of this abstract approach we can give a characterization of the domains of holomorphyin Cn , n ≥ 2. The aforementioned characterization is as follows: adomain in Cn is a domain of holomorphy if and only if it is holomorphically convex. However, holomorphic convexity is a very difficult property to check. This calls for other (equivalent) criteria for a domain in Cn , n ≥ 2, to be a domain of holomorphy. We survey these criteria. The proof of the equivalence of several of these criteria are very technical – requiring methods coming from partial differential equations. We provide those proofs that rely on the first part of our survey: namely, on analytic continuation theorems. If a domain Ω Cn , n ≥ 2, is not a domain of holomorphy, we would still like to explicitly describe a domain strictly larger than Ω to which all functions holomorphic on Ω continue analytically. Aspects of Thullen’s approach are also useful in the quest to construct an explicit strictly larger domain in Cn with the property stated above. The tool used most often in such constructions s called “Kontinuitatssatz”. It has been invoked, without a clear statement, in many works on analytic continuation. The basic (unstated) principle that seems to be in use in these works appears to be a folk theorem. We provide a precise statement of this folk Kontinuitatssatz and give a proof of it.

Quantum trajectories are investigated within the complex quantum Hamilton-Jacobi formalism. A unified description is presented for complex quantum trajectories for one-dimensional time-dependent and time-independent problems. Complex quantum trajectories are examined for the free Gaussian wave packet, the coherent state in the harmonic potential, and the the barrier scattering problems. We analyze the variations of the complex-valued kinetic energy, the classical potential, and the quantum potential along the complex quantum trajectories. For one-dimensional time-independent scattering problems, we demonstrate general properties and similar structures of the complex quantum trajectories and the quantum potentials. In addition, it is shown that a quantum vortex forms around a node in the wave function in complex space, and the quantized circulation integral originates from the discontinuity in the real part of the complex action. Although the quantum momentum field displays hyperbolic flow around a node, the corresponding Polya vector field displays circular flow. Moreover, local topologies of the quantum momentum function and the Polya vector field are thoroughly analyzed near a stagnation point or a pole (including circular, hyperbolic, and attractive or repulsive structures). The local structure of the quantum momentum function and the Polya vector field around a stagnation point are related to the first derivative of the quantum momentum function. However, the magnitude of the asymptotic structures for these two fields near a pole depends only on the order of the node in the wave function. Finally, quantum interference is investigated and it leads to the formation of the topological structure of quantum caves in space-time Argand plots. These caves consist of the vortical and stagnation tubes originating from the isosurfaces of the amplitude of the wave function and its first derivative. Complex quantum trajectories display helical wrapping around the stagnation tubes and hyperbolic deflection near the vortical tubes. Moreover, the wrapping time for a specific trajectory is determined by the divergence and vorticity of the quantum momentum field. The lifetime for interference features is determined by the rotational dynamics of the nodal line in the complex plane. Therefore, these results demonstrate that the complex quantum trajectory method provides a novel perspective for analysis and interpretation of quantum phenomena.
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In this dissertation we consider several problems in classical complex analysis and operator theory. In the first part we study basis properties of a system of complex exponentials with a given frequency sequence. We show that most of these basis properties can be characterized in terms of the invertibility properties of certain Toeplitz operators. We use this reformulation to give a metric description of the radius of l2-dependence. Using similar methods we solve the classical Beurling gap problem in the case of separated real sequences. In the second part we consider the classical Polýa-Levinson problem asking for a description of all real sequences with the property that every zero type entire function which is bounded on such a sequence must be a constant function. We first give a description in terms of injectivity of certain Toeplitz operators and then use this to give a metric description of all such sequences. In the last part we study the spectral changes of a partial isometry under unitary perturbations. We show that all the spectra can be described in terms of the characteristic function of the partial isometry that is being perturbed. Our main tool in the proofs is a Herglotz-type representation for generalized spectral measures. We furthermore use this representation to give a new proof of the classical Naimark's dilation theorem and to generalize Aleksandrov's disintegration theorem.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1992.
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