This thesis contains four articles related to mathematical aspects of Density Functional Theory. In Paper A, the theoretical justification of density methods formulated with current densities is addressed. It is shown that the set of ground-states is determined by the ensemble-representable particle and paramagnetic current density. Furthermore, it is demonstrated that the Schrödinger equation with a magnetic field is not uniquely determined by its ground-state solution. Thus, a wavefunction may be the ground-state of two different Hamiltonians, where the Hamiltonians differ by more than a gauge transformation. This implies that the particle and paramagnetic current density do not determine the potentials of the system and, consequently, no Hohenberg-Kohn theorem exists for Current Density Functional Theory formulated with the paramagnetic current density. On the other hand, by instead using the particle density as data, we show that the scalar potential in the system's Hamiltonian is determined for a fixed magnetic field. This means that the Hohenberg-Kohn theorem continues to hold in the presence of a magnetic field, if the magnetic field has been fixed. Paper B deals with N-representable density functionals that also depend on the paramagnetic current density. Here the Levy-Lieb density functional is generalized to include the paramagnetic current density. It is shown that a wavefunction exists that minimizes the "free" Hamiltonian subject to the constraints that the particle and paramagnetic current density are held fixed. Furthermore, a convex and universal current density functional is introduced and shown to equal the convex envelope of the generalized Levy-Lieb density functional. Since this functional is convex, the problem of finding the particle and paramagnetic current density that minimize the energy is related to a set of Euler-Lagrange equations. In Paper C, an N-representable Kohn-Sham approach is developed that also include the paramagnetic current density. It is demonstrated that a wavefunction exists that minimizes the kinetic energy subject to the constraint that only determinant wavefunctions are considered, as well as that the particle and paramagnetic current density are held fixed. Using this result, it is then shown that the ground-state energy can be obtained by minimizing an energy functional over all determinant wavefunctions that have finite kinetic energy. Moreover, the minimum is achieved and this determinant wavefunction gives the ground-state particle and paramagnetic current density. Lastly, Paper D addresses the issue of a Hohenberg-Kohn variational principle for Current Density Functional Theory formulated with the total current density. Under the assumption that a Hohenberg-Kohn theorem exists formulated with the total current density, it is shown that the map from particle and total current density to the vector potential enters explicitly in the energy functional to be minimized. Thus, no variational principle as that of Hohenberg and Kohn exists for density methods formulated with the total current density. / <p>QC 20140523</p>

Title: A new method for the solution of the Schrödinger equation Author: Jakub Kocák Department: Department of Physical and Macromolecular Chemistry Supervisor: doc. RNDr. Filip Uhlík, Ph.D. Abstract: In this thesis we study method for the solution of time-independent Schrö- dinger equation for ground state. The wave function, interpreted as probability density, is represented by samples. In each iteration we applied approximant of imaginary time propagator. Acting of the operator is implemented by Monte Carlo simulation. Part of the thesis is dedicated to methods of energy calculation from samples of wave function: method based on estimation of value of wave function, method of convolution with heat kernel, method of averaged energy weighed by wave function and exponential de- cay method. The method for the solution was used to find ground state and energy for 6-dimensional harmonic oscillator, anharmonic 3-dimensional octic oscillator and hydrogen atom. Keywords: imaginary time propagation, Monte Carlo method, variational principle, ground state 1

No description available.

Le principe de contraction de Banach, qui garantit l'existence d'un point fixe d'une contraction d'un espace métrique complet à valeur dans lui-même, est certainement le plus connu des théorèmes de point fixe. Dans plusieurs situations concrètes, nous sommes cependant amenés à considérer une contraction qui n'est définie que sur un sous-ensemble de cet espace. Afin de garantir l'existence d'un point fixe, nous verrons que d'autres hypothèses sont évidemment nécessaires. Le théorème de Caristi, qui garantit l'existence d'un point fixe d'une fonction d'un espace métrique complet à valeur dans lui-même et respectant une condition particulière sur d(x,f(x)), a plus tard été généralisé aux fonctions multivoques. Nous énoncerons des théorèmes de point fixe pour des fonctions multivoques définies sur un sous-ensemble d'un espace métrique grâce, entre autres, à l'introduction de notions de fonctions entrantes. Cette piste de recherche s'inscrit dans les travaux très récents de mathématiciens français et polonais. Nous avons obtenu des généralisations aux espaces de Fréchet et aux espaces de jauge de quelques théorèmes, dont les théorèmes de Caristi et le principe variationnel d'Ekeland. Nous avons également généralisé des théorèmes de point fixe pour des fonctions qui sont définies sur un sous-ensemble d'un espace de Fréchet ou de jauge. Pour ce faire, nous avons eu recours à de nouveaux types de contractions; les contractions sur les espaces de Fréchet introduites par Cain et Nashed [CaNa] en 1971 et les contractions généralisées sur les espaces de jauge introduites par Frigon [Fr] en 2000. / The Banach contraction principle, which certifies that a contraction of a complete metric space into itself has a fixed point, is for sure the most famous of all fixed point theorems. However, in many case, the contraction we consider is only defined on a subset of a complete metric space. Of course, to certify that such a contraction has a fixed point, we need to add some restrictions. The Caristi theorem, which certifies the existence of a fixed point of a function of a complete metric space into itself satisfying a particular condition on d(x,f(x)), was later generalized to multivalued functions. By introducing different types of inwardness assumptions, we will be able to state some fixed point theorems for multivalued functions defined on a subset of a metric space. This is related to the recent work of French and Polish mathematicians. We were able to generalize some theorems to Fréchet spaces and gauge spaces such as the Caristi theorems and the Ekeland variational principle. We were also able to generalize some fixed point theorems for functions that are only defined on a subset of a Fréchet space or a gauge space. To do so, we used new types of contractions; contractions on Fréchet spaces introduced by Cain and Nashed [CaNa] in 1971 and generalized contractions on gauge spaces introduced by Frigon [Fr] in 2000.

Neste trabalho, mostramos a existência e multiplicidade de soluções para a seguinte classe de equações elípticas quasilineares { - \'DELTA IND. \'NÜ\' POT. \'upsilon\' + \'|\'upsilon\'| POT. \'NÜ\' - 2 \'upsilon\' = f(x, u), \'upsilon\' \'DIFERENTE\' 0, \'upsilon\' \'PERTENCE A >>: Nu + jujN2 u = f(x; u); x 2 ; u 6= 0; u 2 W1;N( ); onde e um domnio em RN, N 2, N e o operador N-Laplaciano e f e uma func~ao que possui um crescimento crtico exponencial. Para obter nossos resultados utilizamos o Princpio Variacional de Ekeland, Teorema do Passo da Montanha, Categoria de Lusternik- Schnirelman, Ac~ao de Grupo e tecnicas baseadas na Teoria do G^enero. Palavras chaves: Problemas elpticos quasilineares, Metodo Variacional, N-Laplaciano, crescimento crtico exponencial, Princpio Variacional de Ekeland, Categoria de Lusternik- Schnirelman, Desigualdade de Trudinger-Moser / In this work, we show the existence and multiplicity of solutions for the following class of quasilinear elliptic equations { - \'DELTA\' IND. \'NÜ\' \'upsilon\'\' + |\'upsilon\'| POT. \'NÜ\' - 2 = f(x, \'upsilon\'), x \"IT BELONGS\' \'OMEGA\', \'upsilon\' \'DIFFERENT\' 0, \'upsilon\' \'IT BELONGS\' W POT. 1, \'NÜ\' ( OMEGA), where \'OMEGA\' is a domain in \' R POT. \'NÜ\' > OR = 2, \'DELTA\' IND. \'NÜ\' is the N-Laplacian operator and f is a function with exponential critical growth. To obtain our results we utilize the Ekeland Variational Principle, the Mountain Pass Theorem, Lusternik-Schnirelman of Category, Group Action and techniques based on Genus Theory

Diese Arbeit befasst sich mit der Konstruktion verbesserter interpolierender Mesonenfelder in der Gitter-QCD. Sie hat das primäre Ziel, Korrelationsfunktionen mit einem deutlich reduzierten Beitrag des ersten angeregten Mesonenzustandes zu erhalten, um eine sicherere Bestimmung von Massen und Zerfallskonstanten der Mesonen zu ermöglichen. Eine Basis solcher interpolierender Mesonen-Randfelder wird im Schrödinger Funktional in der gequenchten Approximation benutzt. Verbesserte interpolierende Felder zur Bestimmung spektraler Eigenschaften leichter pseudoskalarer Mesonen sowie des B--Mesonensystems (letzteres wird in führender Ordnung der HQET behandelt) werden auf mehreren Wegen gewonnen. Ein Hilfsmittel, verbesserte Felder zu konstruieren, ist das Variationsprinzip. Es wird auf Matrizen von Rand-Rand-Korrelationsfunktionen angewandt. Darüber hinaus werden alternative Analysemethoden vorgestellt. Sie erlauben sowohl die Abschätzung der Grundzustandsenergie als auch der Energielücke zum ersten radial angeregten Zustand. Die Untersuchung des B-Mesonensystems ist in vielfacher Hinsicht interessant. Zum einen werden sie in sogenannten B-Fabriken, wie z. B. im BaBar- und Belle-Experiment, in grosser Zahl erzeugt, um ihre charakteristischen Eigenschaften (Masse, Zerfallsbreiten, CP-Symmetrie verletzende Zerfälle usw.) genau zu messen. Zum anderen müssen die von der Theorie vorhergesagten auftretenden Phänomene, wie z. B. die CP-Verletzung, auch verstanden werden. Die Methoden der Gittereichtheorie können unter anderem dabei helfen, bestehende Unsicherheiten in CKM-Matrixelementen durch nicht-perturbative Bestimmungen hadronischer Massen, Zerfallskonstanten usw. zu reduzieren. / The general aim of this thesis is to probe several methods to extract low-energy quantities (masses, decay constants, ...) more reliably in lattice gauge theory. We will investigate how to suppress contributions to correlation functions from the first excited meson state. We will show how to construct so-called improved meson interpolating fields, as they have only small contributions from the first excited meson state, from a basis of interpolating fields at the Schrödinger functional boundaries. The variational principle is applied to correlation matrices that are built up from boundary-to-boundary correlation functions. It will deliver information about the lowest-lying meson states in the considered channel. We also investigate the possibility to cancel the first excited state contribution by means of an alternative method. Moreover, an alternative way to extract the mass gap between the ground and the first excited state will be presented. Monte-Carlo simulations at several lattice spacings are performed in the ''quenched approximation''. Spectral properties of light-light and static-light pseudoscalar mesons are investigated. The first type is realised by two mass-degenerate quarks at about the strange quark mass, the second type by a light quark with the mass of the strange quark and an infinitely heavy b-quark. The light-light channel describes unphysically heavy pions and the static-light one is an approximation for the Bs-meson. The investigation of the latter case is particularly interesting since so-called B--factories, such as BaBar and Belle, are gathering physical information about masses, decay modes and CP--violating effects in the B--meson system.

Le principe de contraction de Banach, qui garantit l'existence d'un point fixe d'une contraction d'un espace métrique complet à valeur dans lui-même, est certainement le plus connu des théorèmes de point fixe. Dans plusieurs situations concrètes, nous sommes cependant amenés à considérer une contraction qui n'est définie que sur un sous-ensemble de cet espace. Afin de garantir l'existence d'un point fixe, nous verrons que d'autres hypothèses sont évidemment nécessaires. Le théorème de Caristi, qui garantit l'existence d'un point fixe d'une fonction d'un espace métrique complet à valeur dans lui-même et respectant une condition particulière sur d(x,f(x)), a plus tard été généralisé aux fonctions multivoques. Nous énoncerons des théorèmes de point fixe pour des fonctions multivoques définies sur un sous-ensemble d'un espace métrique grâce, entre autres, à l'introduction de notions de fonctions entrantes. Cette piste de recherche s'inscrit dans les travaux très récents de mathématiciens français et polonais. Nous avons obtenu des généralisations aux espaces de Fréchet et aux espaces de jauge de quelques théorèmes, dont les théorèmes de Caristi et le principe variationnel d'Ekeland. Nous avons également généralisé des théorèmes de point fixe pour des fonctions qui sont définies sur un sous-ensemble d'un espace de Fréchet ou de jauge. Pour ce faire, nous avons eu recours à de nouveaux types de contractions; les contractions sur les espaces de Fréchet introduites par Cain et Nashed [CaNa] en 1971 et les contractions généralisées sur les espaces de jauge introduites par Frigon [Fr] en 2000. / The Banach contraction principle, which certifies that a contraction of a complete metric space into itself has a fixed point, is for sure the most famous of all fixed point theorems. However, in many case, the contraction we consider is only defined on a subset of a complete metric space. Of course, to certify that such a contraction has a fixed point, we need to add some restrictions. The Caristi theorem, which certifies the existence of a fixed point of a function of a complete metric space into itself satisfying a particular condition on d(x,f(x)), was later generalized to multivalued functions. By introducing different types of inwardness assumptions, we will be able to state some fixed point theorems for multivalued functions defined on a subset of a metric space. This is related to the recent work of French and Polish mathematicians. We were able to generalize some theorems to Fréchet spaces and gauge spaces such as the Caristi theorems and the Ekeland variational principle. We were also able to generalize some fixed point theorems for functions that are only defined on a subset of a Fréchet space or a gauge space. To do so, we used new types of contractions; contractions on Fréchet spaces introduced by Cain and Nashed [CaNa] in 1971 and generalized contractions on gauge spaces introduced by Frigon [Fr] in 2000.

Light-harvesting in nature is known to work differently than conventional man-made solar cells. Recent studies found electronic excitations, delocalised over several chromophores, and a soft, vibrating structural environment to be key schemes that might protect and direct energy transfer yielding increased harvest efficiencies even under adversary conditions. Unfortunately, testing realistic models of noise assisted transport at the quantum level is challenging due to the intractable size of the environmental wave function. I developed a powerful tree tensor network states (TTNS) method that finds an optimally compressed explicit representation of the combined electronic and vibrational quantum state. With TTNS it is possible to simulate exciton-phonon quantum dynamics from small molecules to larger complexes, modelled as an open quantum system with multiple bosonic environments. After benchmarking the method on the minimal spin-boson model by reproducing ground state properties and dynamics that have been reported using other methods, the vibrational quantum state is harnessed to investigate environmental dynamics and its correlation with the spin system. To enable simulations of realistic non-Born-Oppenheimer molecular quantum dynamics, a clustering algorithm and novel entanglement renormalisation tensors are employed to interface TTNS with ab initio density functional theory (DFT). A thereby generated model of a pentacene dimer containing 252 vibrational normal modes was simulated with TTNS reproducing exciton dynamics in agreement with experimental results. Based on the environmental state, the (potential) energy surfaces, underlying the observed singlet fission dynamics, were calculated yielding unprecedented insight into the super-exchange mediated avoided crossing mechanism that produces ultrafast and high yield singlet fission. This combination of DFT and TTNS is a step towards large scale material exploration that can accurately predict excited states properties and dynamics. Furthermore, application to biomolecular systems, such as photosynthetic complexes, may give valuable insights into novel environmental engineering principles for the design of artificial light-harvesting systems.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-06T15:14:18Z No. of bitstreams: 1 ROMILDO NASCIMENTO DE LIMA - DISSERTAÇÃO PPGMAT 2013..pdf: 632336 bytes, checksum: 5661cad2fea6b9bb474c05bca0983c4b (MD5) / Made available in DSpace on 2018-08-06T15:14:18Z (GMT). No. of bitstreams: 1 ROMILDO NASCIMENTO DE LIMA - DISSERTAÇÃO PPGMAT 2013..pdf: 632336 bytes, checksum: 5661cad2fea6b9bb474c05bca0983c4b (MD5) Previous issue date: 2013-02 / Capes / Neste trabalho estaremos interessados em estudar resultados de existência e não existência de solução, comportamento do funcional energia e condição de Palais-Smale para sistemas de equações do tipo Schrödinger-Poisson; usaremos o método variacional. E, as soluções são pontos críticos do funcional energia associado ao problema. Para alcançar nossos objetivos, será fundamental o estudo das variedades de Ruiz e de Nehari, o Princípio Variacional de Ekeland, o teorema do Passo da Montanha, e o lema Concentração de Compacidade. / In this work we are interested in studying the results of existence and nonexistence of solution, behavior of the energy functional and Palais-Smale condition for systems of equations of the type Schrödinger-Poisson; by using variational approach. In fact the solutions are critical points of the energy functional associated with the problem. To achieve our goals, it is essential to study the Manifolds of Ruiz and Nehari, the Ekeland Variational Principle, the Mountain Pass theorem, and the Concentration-Compactness argument.

Made available in DSpace on 2015-05-15T11:46:04Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 695566 bytes, checksum: 26f7afc275ad83fa634352b9d522415e (MD5) Previous issue date: 2012-04-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this dissertation, we study the existence of two types of non-negative weak solutions for a class of problems of Schrodinger-Poisson type. This kind of problem models, for example, several physical phenomena in quantum mechanics. Initially, by minimization arguments, Splitting Lemma and the Variational Principle of Ekeland we find a weak solution that minimizes the minimum energy level associated to the variety of Nehari N. This is the so-called ground state solution. Afterwards we will find, by using the Linking Theorem, a strictly positive weak solution which is not a ground state solution: the so-called bound state solution. / Nesta dissertação, estudaremos a existência de dois tipos de soluções fracas não negativas para uma classe de problemas do tipo Schrödinger-Poisson, os quais modelam fenômenos físicos, por exemplo, em Mecânica Quântica. Inicialmente, encontraremos através de argumentos de minimização, do Lema Splitting e do Princípio Variacional de Ekeland, uma solução fraca que minimiza o nível de energia mínima associado a variedade de Nehari N. Tal solução é denominada do tipo ground state. Em seguida, encontraremos através do Teorema de Linking, uma solução fraca estritamente positiva que não é do tipo ground state. Tal solução é denominada do tipo bound state.