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181	The Diamond Lemma for Power Series Algebras Hellström, Lars January 2002 (has links) The main result in this thesis is the generalisation of Bergman's diamond lemma for ring theory to power series rings. This generalisation makes it possible to treat problems in which there arise infinite descending chains. Several results in the literature are shown to be special cases of this diamond lemma and examples are given of interesting problems which could not previously be treated. One of these examples provides a general construction of a normed skew field in which a custom commutation relation holds. There is also a general result on the structure of totally ordered semigroups, demonstrating that all semigroups with an archimedean element has a (up to a scaling factor) unique order-preserving homomorphism to the real numbers. This helps analyse the concept of filtered structure. It is shown that whereas filtered structures can be used to induce pretty much any zero-dimensional linear topology, a real-valued norm suffices for the definition of those topologies that have a reasonable relation to the multiplication operation. The thesis also contains elementary results on degree (as of polynomials) functions, norms on algebras (in particular ultranorms), (Birkhoff) orthogonality in modules, and construction of semigroup partial orders from ditto quasiorders. Mathematical analysis diamond lemma power series algebra Gröbner basis embedding into skew fields archimedean element in semigroup q-deformed Heisenberg--Weyl algebra polynomial degree ring norm Birkhoff orthogonality filtered structure Matematisk analys Mathematical analysis Analys
182	Theoretical Studies of Two-Dimensional Magnetism and Chemical Bonding Grechnyev, Oleksiy January 2005 (has links) This thesis is divided into two parts. In the first part we study thermodynamics of the two-dimensional Heisenberg ferromagnet with dipolar interaction. This interaction breaks the conditions of the Mermin-Wagner theorem, resulting in a finite transition temperature. Our calculations are done within the framework of the self-consistent spin-wave theory (SSWT), which is modified in order to include the dipolar interaction. Both quantum and classical versions of the Heisenberg model are considered. The second part of the thesis investigates the chemical bonding in solids from the first principles calculations. A new chemical bonding indicator called balanced crystal orbital overlap population (BCOOP) is developed. BCOOP is less basis set dependent than the earlier indicators and it can be used with full-potential density-functional theory (DFT) codes. We apply BCOOP formalism to the chemical bonding in the high-T_c superconductor MgB2 and the theoretically predicted MAX phase Nb3SiC2. We also study how the chemical bonding results in a repulsive hydrogen–hydrogen interaction in metal hydrides. The role of this interaction in the structural phase transition in Ti3SnHx is investigated. Physics spin Hamiltonians quantized spin models Heisenberg model spin waves self-consistent spin-wave theory dipolar interaction density functional theory chemical bonding overlap population MAX phases metal hydrides Fysik Physics Fysik
183	Influence of Global Composition and Local Environment on the Spectroscopic and Magnetic Properties of Metallic Alloys Olovsson, Weine January 2005 (has links) Theoretical investigations of spectroscopic and magnetic properties of metallic systems in the bulk, as well as in nanostructured materials, have been performed within the density functional theory. The major part of the present work studies the differences between binding energies of electrons tightly bound to the atoms, the so-called core electrons (in contrast with the valence electrons), that is, core-level binding energy shift (CLS). By comparison between corresponding elemental core-levels for atoms situated in different chemical environments we obtain fundamental understanding of bonding properties of materials. The method of choice was the complete screening picture, which includes initial and final state effects on the same footing. The usefulness of CLS stems from that it is sensitive to differences in the chemical environment of an atom, which can be affected on one hand by the global composition of e.g. disordered materials, surfaces and interfaces, and on the other hand by the very local environment around an atom. Here CLSs have been obtained for both components in the fcc random alloys AgPd, CuPd, CuNi, CuPt, CuAu, PdAu, NiPd and NiPt. Moreover the model was extended to the Auger kinetic energy shift for the LMM Auger transition in AgPd alloys. Studies were also applied to the near surface and interface regions of PdMn nano structures on Pd(100), thin CuPd and AgPd films on inert Ru(0001), and at interfaces. The disorder broadening on CLS due to local environment effects was calculated in selected alloys. A part of the thesis concern investigations related to the magnetic ordering in Invar alloys, including the influence of local environment effects. A study was made for the dependence of effective exchange parameter on the electron concentration, volume and local chemical composition. Physics core level shift random alloy first principles simulations density functional theory auger kinetic energy Invar alloys exchange parameter classical Heisenberg Hamiltonian complete screening transition state disorder broadening Fysik Physics Fysik
184	The Quantum Dialectic Kelley, Logan 15 May 2011 (has links) A philosophic account of quantum physics. The thesis is divided into two parts. Part I is dedicated to laying the groundwork of quantum physics, and explaining some of the primary difficulties. Subjects of interest will include the principle of locality, the quantum uncertainty principle, and Einstein's criterion for reality. Quantum dilemmas discussed include the double-slit experiment, observations of spin and polarization, EPR, and Bell's theorem. The first part will argue that mathematical-physical descriptions of the world fall short of explaining the experimental observations of quantum phenomenon. The problem, as will be argued, is framework of the physical descriptive schema. Part I includes in-depth discussions of mathematical principles. Part II will discuss the Copenhagen interpretation as put forth by its founders. The Copenhagen interpretation will be expressed as a paradox: The classical physical language cannot describe quantum phenomenon completely and with certainty, yet this language is the only possible method of articulating the physical world. The paradox of Copenhagen will segway into Kant's critique of metaphysics. Kant's understanding of causality, things-in-themselves, and a priori synthetic metaphysics. The thesis will end with a conclusion of the quantum paradox by juxtaposing anti-materialist Martin Heidegger with quantum founder Werner Heisenberg. Our conclusion will be primarily a discussion of how we understand the world, and specifically how our understanding of the world creates potential for truth. quantum physics philosophy heisenberg heidegger uncertainty principle kant Continental Philosophy Discrete Mathematics and Combinatorics Epistemology Logic and foundations of mathematics Metaphysics Other Physics Other Statistics and Probability Philosophy Philosophy of Language Philosophy of Science Quantum Physics
185	Electronic structure and exchange integrals of low-dimensional cuprates Rosner, Helge 19 September 1999 (has links) (PDF) The physics of cuprates is strongly influenced by the dimension of the cooper-oxygen network in the considered crystals. Due to the rich manifoldness of different network geometries realized by nature, cuprates are ideal model systems for experimental and theoretical studies of low-dimensional, strongly correlated systems. The dimensionality of the considered model compounds varies between zero and three with a focus on one- and two-dimensional compounds. Starting from LDA band structure calculations, the relevant orbitals for the low-energy physics have been characterized together with a discussion of the chemical bonding in the investigated compounds. By means of a systematic approach for various compounds, the influence of particular structural components on the electronic structure could be concluded. For the undoped cuprate compounds, paramagnetic LDA band structure calculations yield a metallic groundstate instead of the experimentally observed insulating behavoir. The strong correlations were taken into account using Hubbard- or Heisenberg-like models for the investigation of the magnetic couplings in cuprates. The necessary parameters were obtained from tight-binding parameterizations of LDA band structures. Finallly, several ARPES as well as XAS measurements were interpreted. The present work shows, that the combination of experiment, LDA, and model calculations is a powerful tool for the investigation of the electronic structure of strongly correlated systems. nicht angegeben Heisenberg model Hubbard model LDA bandstructure cuprates exchange integrals spectroscopy spin 1/2 systems tightbinding model ddc:29 rvk:UP 3600 Cuprate Elektronenstruktur Hochtemperatursupraleiter Niederdimensionales System Photoelektronenspektroskopie Röntenabsorptionsspektroskopie
186	Localisation et décroissance des champs de la mécanique des fluides et des plasmas. Espaces fonctionnels associés à une famille de champs de vecteurs. Vigneron, Francois 22 November 2006 (has links) (PDF) La première partie est consacrée à l'étude du comportement asymptotique des solutions de Navier-Stokes incompressible à l'infini de la variable d'espace. On obtient des résultats optimaux de propagation de la décroissance en terme d'espaces à poids, ainsi qu'un developpement asymptotique de la vitesse et de la pression analogue à la loi de Bernoulli. La théorie s'étend à un modèle de la MHD.<br />La seconde partie est consacrée à l'étude des espaces de Sobolev associés à une famille de champs de vecteurs, de type sous-elliptique. Les principaux résultats sont la description des régularités fractionnaires avec la distance de Carnot, la démonstration d'inégalités de Hardy et, dans le cas du groupe de Heisenberg, la théorie des traces sur une hypersurface caractéristique générique. [MATH] Mathematics LOCALISATION DECROISSANCE COMPORTEMENT ASYMPTOTIQUE NAVIER-STOKES MAGNETO-HYDRODYNAMIQUE (MHD) ESPACES A POIDS ESPACES DE SOBOLEV REGULARITES FRACTIONNAIRES CONDITION DE CROCHET (HORMANDER) SOMME DE CARRES DE CHAMPS DE VECTEURS INEGALITE DE HARDY TRACES GROUPE DE HEISENBERG
187	Phase diagrams of two-dimensional frustrated spin systems / Phasendiagramme für zweidimensionale frustrierte Spinsysteme Kalz, Ansgar 22 March 2012 (has links) No description available. 530 Physik RDI 800 Physics korreliert magnetisch zweidimensional frustriert Spinmodell Phasenübergang Grundzustand Isingmodell Heisenbergmodell Quantenfluktuation Quadratgitter Honeycombgitter correlated magnetic two-dimensional frustrated spin model Ising Heisenberg ground state phase transition quantum fluctuations square lattice honeycomb lattice 33.10 33.23 33.61 33.64
188	Mathematical Foundations of Quantum Mechanics / Kvantfysikens Matematiska Grunder Israelsson, Anders January 2013 (has links) No description available. Mathematics Physics Quantum Mechanics Uncertainty Principle Functional Self-adjoint Hermitian Hilbertspace Dynamics Commutator Hydrogen Atom Lower Bound Estimate Laplacian Matematik Fysik Kvantfysik Kvantmekanik Heisenberg Obestämdhetsrelation Schrödinger Planck Funktional Analys Självadjungerad Hermitisk Operator Hilbertrum Hamiltonian Dynamik Kommutator Väteatom Nedåtbegränsning Laplace
189	Approche liens de valence de la physique de basse énergie des systèmes antiferromagnétiques Schwandt, David 13 July 2011 (has links) (PDF) L'objet de cette thèse est le traitement du modèle de Heisenberg antiferromagnétique dans la base de liens de valence, qui permet d'en décrire la physique de basse énergie. Le manuscrit est organisé en deux parties : dans la première nous utilisons le concept de fidélité afin de détecter les transitions de phases quantiques. Nous démontrons notamment que cette quantité est accessible dans un algorithme de Monte Carlo quantique, formulé dans la base de liens de valence, permettant ainsi de calculer la fidélité sur des systèmes de grande taille. La deuxième partie vise à développer l'idée initiale de Rokhsar et Kivelson, qui a pour but de transformer un modèle de Heisenberg en un modèle de dimères quantiques, généralement moins complexe d'un point de vue numérique. Après une dérivation rigoureuse, cette technique est appliquée au réseau kagomé et permet d'établir l'existence d'un point tricritique au voisinage du modèle initial. La même méthode est ensuite utilisée afin de traiter le modèle J1-J2-J3 sur le réseau hexagonal et démontre l'existence d'une phase plaquette dans un domaine de paramètres déterminé. Physique de la matière condensée Modèle de Heisenberg Théorie de liens de valence Monte Carlo quantique
190	Μελέτη μονοδιάστατων μαγνητικών αλυσίδων με μεθοδολογία κβαντικού Monte Carlo Ανδροβιτσανέας, Πέτρος 20 April 2011 (has links) Στην συγκεκριμένη εργασία ασχολούμαστε με την μελέτη θερμικά σύμπλεκτων (entangled) καταστάσεων πολλών κβαντικών bit (qubit) σε διάφορα μοντέλα Heisenberg με την μέθοδο Monte Carlo (MC). Αρχικά χρησιμοποιώντας τον μετασχηματισμό Suzuki-Trotter μετατρέπουμε την κβαντική μονοδιάστατη αλυσίδα των spin (μοντέλα Ising, Heisenberg με και χωρίς μαγνητικό πεδίο στις διευθύνσεις x,y,z) σε κλασικό δισδιάστατο πλέγμα. Εξετάζουμε την συμπεριφορά του συγκεκριμένου μετασχηματισμού για το αντισιδηρομαγνητικό Heisenberg ΧΧΧ μοντέλο, για το σιδηρομαγνητικό Heisenberg μοντέλο (ΧΧΧ και ΧΥΖ) χωρίς και με μαγνητικό πεδίο στις διευθύνσεις x,y,z για διάφορα μήκη της αλυσίδας, διαφορετικές διαστάσεις Trotter και διαφορετικό αριθμό Monte Carlo βημάτων (MCΒήματα). Μελετάμε την συμπεριφορά της θερμοχωρητικότητας, της ενέργειας, της μαγνητικής επιδεκτικότητας και της μαγνήτισης στις διευθύνσεις x,y,z. Επιβεβαιώνουμε την σωστή συμπεριφορά τους με βάση τα αναλυτικά αποτελέσματα. Τέλος γνωρίζοντας, ότι η κλασική συσχέτιση είναι το κάτω όριο της ποσότητας Localizable Entanglement, και ότι η ποσότητα Entanglement of Assistance είναι το πάνω όριο, εκτιμούμε για τα ίδια μοντέλα τη συμπεριφορά των ορίων και προσπαθούμε να εκτιμήσουμε το μήκος σύμπλεξης (Entanglement Length) για διάφορες θερμοκρασίες. / In the present Master Thesis we study the thermal entangled states of many qubits in a variety of Heisenberg models with the deployment of the Monte Carlo(MC) method. Initially we are using the Suzuki-Trotter decomposition in order to convert the one dimensional spin chain(models Ising, Heisenberg with and without magnetic field in the x,y,z axis) into a classical two dimensional lattice. We examine the behavior of the latter decomposition for the antiferromagnetic Heisenberg XXX model, the ferromagnetic Heisenberg model (XXX and XYZ) with or without magnetic field in the axis x,y,z for different chain lengths, Trotter dimensions and number of Monte Carlo Steps (MCSteps). We investigate the behavior of the following quantities: specific heat, energy, susceptibility and magnetization in the axis x,y,z. We confirm their proper behavior comparing to analytical and arithmetic results. Finally knowing that the maximum classical correlation function is the lower limit of the quantity Localizable Entanglement (LE) and that the quantity Entanglement of Assistance is the upper limit, we evaluate for the same models the behavior of the limits and we try to evaluate the Entanglement Length for a variety of temperatures. Κβάντο Συσχέτιση Σύμπλεξη Σιδηρομαγνητικό Αντισιδηρομαγνητικό Επιδεκτικότητα Θερμοχωρητικότητα Κβαντικό bit 530.133 Magnetic one dimensional chain Quantum Correlation Entanglement Heisenberg Ising Spin Ferromagnetic Antiferromagnetic Monte Carlo Trotter Susceptibility Specific heat Qubit

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