Hamiltonian Systems
Mostrando 37-48 de 82 artigos, teses e dissertações.
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37. InformaÃÃo quÃntica e emaranhamento: uma abordagem usando Ãlgebra geomÃtrica
We studied the quantum entanglement as a quantum computation and quantum information tool. This research focused on the bipartite entanglement found between two qubits of a Heisenberg hamiltonian. The choice of this hamiltonian was motivated by the fact that it can be simulated by many distinct physical systems. Besides, the control of its parameters during
Publicado em: 2007
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38. Local and global symmetries in gauge theories / Simetrias globais e locais em teorias de calibre
This thesis deals with the geometric formulation of classical gauge theories, or Yang-Mills theories, regarded as an important class of models that must be included in any attempt to establish a general mathematical framework for classical field theory. Such a formulation must come in (at least) two variants: the hamiltonian version which has gone through a
Publicado em: 2007
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39. Nonhomogeneous semilinear elliptic systems / Sistemas elipticos semilineares não-homogeneos
Neste trabalho consideramos duas classes de sistemas não homogêneos sendo que em certos casos uma dessas classes tranforma-se em um sistema gradiente, enquanto que a outra em um sistema de tipo Hamiltoniano. Analisamos as questões de existência, não-existênca, unicidade e multiplicidade de solu-ções.Para obter nossos resultados empregamos o método d
Publicado em: 2007
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40. Processos estocásticos e interações de longo alcance
The long range interacting systems are very interesting because of their evolutive behavior towards thermodynamic equilibrium. They pass through a violent relaxation during a short period of time in a quasi-stationary state with anomalous diffusion. After that, it evolves very slowly to a gaussian state in which it presents a normal diffusion. Using simulati
Publicado em: 2007
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41. DISSIPAÇÃO EM MODOS ACOPLADOS
The implementation of processes of Quantum Computation as well as the transmission and quantum information control in realistic physical systems, must take in account the effects of the coupling of the systems with the environment, represented by thermal reservoirs. In this work it is considered the study of the effects of the environment in the quantum prop
Publicado em: 2007
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42. Dois Elétrons em cadeias cristalinas e aperiódicas: efeito de campo elétricos.
Recently much attention was drived to the interplay between dynamical localization and electron-electron interaction. In this master degree thesis we contribute to futher understanding of the phenomenon of electronic Bloch oscillations in both periodic and apperiodic low-dimensional systems with two interacting electrons. We followed two distinct quantum for
Publicado em: 2007
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43. Estabilidade de equilíbrios de sistemas hamiltonianos autônomos e periódicos
Nesta tese, fazemos um estudo detalhado da estabilidade de equilíbrios de sistemas Hamiltonianos autônomos e periódicos com n graus de liberdade que possuem todos os autovalores imaginários puros nos casos de existência de ressonâncias simples e múltiplas . Observando que o conjunto das ressonâncias possui estrutura de módulo finitamente gerado, car
Publicado em: 2007
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44. Microscopic theory of spin waves in magnetic nanowires / Teoria microscÃpica de ondas de spin em nanofios magnÃticos
The dynamical behavior of spins in magnetic materials is affected by its geometry and dimensionality. One can find several new results in the literature exploiting the magnetic properties of low dimension systems with different geometries, since the development of new devices such as: nanosensors, high density magnetic storage, etc., is closely related to ne
Publicado em: 2007
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45. Fases geométricas e invariantes dinâmicos em mecânica quântica
The increasing interest to understand the geometric phases (mainly due to the possi- bility to achieve geometric quantum computation robust against some kind of errors) and the search for new techniques to solve time-dependent problems in Quantum Mechanics, are the topics approached in this thesis. i) Within nowadays technology, it is presented a scheme to c
Publicado em: 2007
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46. What do Monte Carlo simulations tell us about compressible Ising models?
Monte Carlo simulations have begun to illuminate the nature of phase transitions and universality classes for compressible Ising models. A comprehensive analysis of a Landau-Ginsburg Wilson hamiltonian for systems with elastic degrees of freedom predicts that there should be four cases with different behavior, depending upon symmetries and thermodynamic cons
Brazilian Journal of Physics. Publicado em: 2006-09
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47. BifurcaÃÃo de SoluÃÃes PeriÃdicas
The purpose of this work is to study two bifurcation methods of differential equations periodic solutions. These methods leave to find periodic solutions of a perturbed system, when all solutions of non-perturbed system are periodic. We can apply this idea to determine the existence of closed geodesics in surfaces, which are perturbations of others surfaces,
Publicado em: 2006
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48. Correlations and interferences in atomic systems of cold Bose Einstein condensates / Correlações e interferência de sistemas atômicos de Bose-Einstein frios
This work consists of a theoretical study of the coexistance of coupled atomic Bose-Einstein condensates. These mixed condensates can consist of atoms of the same element in different hyperfine internal states. A different situation is that in which an atom in one internal state can ocupate different single particle external states. The similarities and diff
Publicado em: 2006