Semiclassical Methods
Mostrando 1-10 de 10 artigos, teses e dissertações.
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1. Instantonic methods for quantum tunneling in finite size
The instantonic approach for a Φ4 model potential is reexamined in the asymptotic limit. The path integral of the system is derived in semiclassical approximation expanding the action around the classical background. It is shown that the singularity in the path integral, arising from the zero mode in the quantum fluctuation spectrum, can be tackled only ass
Brazilian Journal of Physics. Publicado em: 2009-12
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2. 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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3. Dissipação, termalização e descoerencia via acoplamento caotico / Dissipation, thermalization and decoherence through chaotic coupling
We study here how and under which conditions a chaotic system with only two degrees of freedom can produce irreversible phenomena such as dissipation, thermalization and, from the quantum point of view, decoherence in a simple system coupled to it. In the classical formulation of the problem, we describe analytically the behavior of the energy ux in Linear R
Publicado em: 2006
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4. Transporte em nanoestruturas: mÃtodos de movimento Browniano e teoria de circuitos
The results presented in this thesis can be divided into two parts. In the first one we study a class of Brownian motion ensembles (BME) obtained from the general theory of matricial Markovian stochastic processes of random matrix theory. The ensembles are characterized by a Fokker-Planck equation and are closely related to Hamiltonians of Calogero-Sutherlan
Publicado em: 2006
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5. Validity of semiclassical gravity in the stochastic gravity approach
In semiclassical gravity the back-reaction of the classical gravitational field interacting with quantum matter fields is described by the semiclassical Einstein equations. A criterion for the validity of semiclassical gravity based on the stability of the solutions of the semiclassical Einstein equations with respect to quantum metric perturbations is discu
Brazilian Journal of Physics. Publicado em: 2005-06
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6. A semi-classical picture of the charmonium-hadron interaction
In this work, we present calculations for the charmonium-hadron cross section. The hadron is represented by an external color field and the charmonium is represented by a small color dipole. Using high-energy approximations we compute the relevant cross sections, which agree with results obtained with other methods.
Brazilian Journal of Physics. Publicado em: 2004-03
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7. Coherent states: the symplectic goup and generalizations / Estados coerentes: o grupo simplético e generalizações.
The subject of the Thesis was the aplication of the coherent states theory to non-trivial quantum systems. Starting from the general definition of coherent states for compact Lie groups, we made a detailed investigation of the construction of these states and its properties in the case of the unitary symplectic group Sp(4), which is extremely important in bo
Publicado em: 2003
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8. New method for obtaining complex roots in the semiclassical coherent-state propagator formula
A semiclassical formula for the coherent-state propagator requires the determination of specific classical paths inhabiting a complex phase-space and governed by a Hamiltonian flux. Such trajectories are constrained to special boundary conditions which render their determination difficult by common methods. In this paper we present a new method based on Rung
Braz. J. Phys.. Publicado em: 2001-09
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9. Bilhares quanticos como modelo para um gas mesoscopico magnetizado
During the last years, mesoscopic systems have been attracting much interest in Theoretical Physics, due to the implementation of important theories in this field such as the semiclassical theory of periodic, classical, orbits. The recent progresses in experimental techniques, in semiconductor materials, showed that the manipulation of real systems with as f
Publicado em: 1998
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10. Teoria da seção de Bogomolny para o estadio
The quarter-stadium can be decomposed into a rectangle and a quarter-circle; in each of these regions the Helmholtz equation is separable. We thus explicitly construct Green functions for both regions and a fully quantum mechanical Bogomolny finite matrix including real and evanescent waves is built. The eigenvalues and the eigenfunctions calculated with ext
Publicado em: 1997