Hunting colored (quantum) butterflies : a geometric derivation of the TKNN-equations

The aim of this introductory chapter is to present the scope of this thesis fixing basic notions and terminology, as well to provide a complete, but non technical, exposition of the main results. Section 1.1 is devoted to a historical review of the quantum Hall effect (QHE), trough main steps that lead to its \u201ctopological interpretation\u201d. The notions of topological quantization and topological quantum numbers are expounded using the Dirac\u2019s monopole as a paradigm....

An Algorithmic Approach to Operator Product Expansions, WW-Algebras and WW-Strings

String theory is currently the most promising theory to explain the spectrum of the elementary particles and their interactions. One of its most important features is its large symmetry group, which contains the conformal transformations in two dimensions as a subgroup. At quantum level, the symmetry group of a theory gives rise to differential equations between correlation functions of observables. We show that these Ward-identities are equivalent to Operator Product Expansions (OPEs), which encode the short-distance singularities of correlation functions with symmetry generators. The OPEs allow us to determine algebraically many properties of the theory under study. We analyse the calculational rules for OPEs, give an algorithm to compute OPEs, and discuss an implementation in Mathematica. There exist different string theories, based on extensions of the conformal algebra to so-called W-algebras. These algebras are generically nonlinear. We study their OPEs, with as main results an efficient algorithm to compute the beta-coefficients in the OPEs, the first explicit construction of the WB_2-algebra, and criteria for the factorisation of free fields in a W-algebra. An important technique to construct realisations of W-algebras is Drinfel'd- Sokolov reduction. The method consists of imposing certain constraints on the elements of an affine Lie algebra. We quantise this reduction via gauged WZNW-models. This enables us in a theory with a gauged W-symmetry, to compute exactly the correlation functions of the effective theory. Finally, we investigate the critical W-string theories based on an extension of the conformal algebra with one symmetry generator of dimension N. We clarify how the spectrum of this theory forms a minimal model of the W_N-algebra.Comment: 127 pages, LaTex, shar-file including readme.txt, 12 latex files, 6 eps files and 6 pcx files, PhD. thesis KU Leuve

Mathematical Economics

This book is devoted to the application of fractional calculus in economics to describe processes with memory and non-locality. Fractional calculus is a branch of mathematics that studies the properties of differential and integral operators that are characterized by real or complex orders. Fractional calculus methods are powerful tools for describing the processes and systems with memory and nonlocality. Recently, fractional integro-differential equations have been used to describe a wide class of economical processes with power law memory and spatial nonlocality. Generalizations of basic economic concepts and notions the economic processes with memory were proposed. New mathematical models with continuous time are proposed to describe economic dynamics with long memory. This book is a collection of articles reflecting the latest mathematical and conceptual developments in mathematical economics with memory and non-locality based on applications of fractional calculus

Etude mathématique de modèles quantiques et classiques pour les matériaux aléatoires à l'échelle atomique

Les contributions de cette thèse portent sur deux sujets.La première partie est dédiée à l'étude de modèles de champ moyen pour la structure électronique de matériaux avec des défauts.Dans le chapitre~ref{chap:ergodic_crystals}, nous introduisons et étudions le modèle de Hartree-Fock réduit (rHF) pour des cristaux désordonnés. Nous prouvons l'existence d'un état fondamental et établissons, pour les interactions de Yukawa (à courte portée), certaines propriétés de cet état. Dans le chapitre~ref{chap:défauts_étendus}, nous considérons des matériaux avec des défauts étendus. Dans le cas des interactions de Yukawa, nous prouvons l'existence d'un état fondamental, solution de l'équation auto-cohérente. Nous étudions également le cas de cristaux avec une faible concentration de défauts aléatoires. Dans le chapitre~ref{chap:numerical_simuation}, nous présentons des résultats de simulations numériques de systèmes aléatoires en dimension un.Dans la deuxième partie, nous étudions des modèles Monte-Carlo cinétique multi-échelles en temps. Nous prouvons, pour les trois modèles présentés au chapitre~ref{chap:kMC}, que les variables lentes convergent, dans la limite de la grande séparation des échelles de temps, vers une dynamique effective. Nos résultats sont illustrés par des simulations numériques.The contributions of this thesis concern two topics.The first part is dedicated to the study of mean-field models for the electronic structure of materials with defects. In Chapter~ref{chap:ergodic_crystals}, we introduce and study the reduced Hartree-Fock (rHF) model for disordered crystals. We prove the existence of a ground state and establish, for (short-range)Yukawa interactions, some properties of this ground state. In Chapter~ref{chap:défauts_étendus}, we consider crystals with extended defects. Assuming Yukawa interactions, we prove the existence of an electronic ground state, solution of the self-consistent field equation. We also investigate the case of crystals with low concentration of random defects. In Chapter~ref{chap:numerical_simuation}, we present some numerical results obtained from the simulation of one-dimensional random systems.In the second part, we consider multiscale-in-time kinetic Monte Carlo models. We prove, for the three models presented in Chapter~ref{chap:kMC}, that in the limit of large time-scale separation, the slow variables converge to an effective dynamics. Our results are illustrated by numerical simulations.CERGY PONTOISE-Bib. electronique (951279901) / SudocSudocFranceF

Chiral Random Matrix Theory: Generalizations and Applications

Kieburg M. Chiral Random Matrix Theory: Generalizations and Applications. Bielefeld: Fakultät für Physik; 2015