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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Termoestat?stica qu?ntica: uma abordagem via estat?sticas n?o-gaussianas

Santos, Alyson Paulo 16 March 2012 (has links)
Made available in DSpace on 2015-03-03T15:16:25Z (GMT). No. of bitstreams: 1 AlysonPS_TESE.pdf: 964551 bytes, checksum: c9d496a0da4f410a6e8efa100d961e64 (MD5) Previous issue date: 2012-03-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Considering a quantum gas, the foundations of standard thermostatistics are investigated in the context of non-Gaussian statistical mechanics introduced by Tsallis and Kaniadakis. The new formalism is based on the following generalizations: i) Maxwell- Boltzmann-Gibbs entropy and ii) deduction of H-theorem. Based on this investigation, we calculate a new entropy using a generalization of combinatorial analysis based on two different methods of counting. The basic ingredients used in the H-theorem were: a generalized quantum entropy and a generalization of collisional term of Boltzmann equation. The power law distributions are parameterized by parameters q;, measuring the degree of non-Gaussianity of quantum gas. In the limit q ?1; ?0, the gaussian thermostatistics is recovered. A complementary study is related to a perfect gas in the context of general relativity. Using the non-Gaussian effects on the concept of entropy flux, and on the collisional term of the Boltzmann equation, we generalize the H-theorem within the Tsallis and Kaniadakis frameworks. In the first one, the nonextensive parameter is constrained to the interval [0,2] / Considerando um g?s qu?ntico, os fundamentos da termoestat?stica padr?o s?o investigados no contexto da mec?nica estat?stica n?o-gaussiana introduzida por Tsallis e Kaniadakis. O novo formalismo ? baseado nas seguintes generaliza??es: i) entropia de Maxwell-Boltzmann-Gibbs e ii) dedu??o do Teorema-H. Com base neste estudo, calculamos uma nova entropia usando a generaliza??o da an?lise combinat?ria baseadas em dois diferentes m?todos de contagem. Os ingredientes b?sicos usados no teorema-H foram: uma entropia qu?ntica generalizada e uma generaliza??o do termo colisional da equa??o de Boltzmann. As distribui??es lei de pot?ncia calculadas s?o parametrizadas pelos par?metros q; , medindo o grau de n?o-gaussianidade do sistema. No limite q ?1; ?0, a termoestat?stica gaussiana ? recuperada. Um estudo complementar est? relacionado com um g?s perfeito no contexto da relatividade geral. Utilizando os efeitos n?o-gaussiano no conceito de fluxo de entropia, e no termo colisional da equa??o de transporte de Boltzmann, n?s generalizamos o teorema- H nos formalismos de Tsallis e Kaniadakis. No formalismo de Tsallis, o par?metro n?o extensivo est? restrito ao intervalo [0,2]
2

Fundamenta??o cin?tica da estat?stica n?o gaussiana : efeitos em politr?picas

Bento, Eli?ngela Paulino 19 September 2011 (has links)
Made available in DSpace on 2015-03-03T15:15:26Z (GMT). No. of bitstreams: 1 EliangelaPB_DISSERT.pdf: 614353 bytes, checksum: 050737d0ef158e6082d81254619adac0 (MD5) Previous issue date: 2011-09-19 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Considering a non-relativistic ideal gas, the standard foundations of kinetic theory are investigated in the context of non-gaussian statistical mechanics introduced by Kaniadakis. The new formalism is based on the generalization of the Boltzmann H-theorem and the deduction of Maxwells statistical distribution. The calculated power law distribution is parameterized through a parameter measuring the degree of non-gaussianity. In the limit = 0, the theory of gaussian Maxwell-Boltzmann distribution is recovered. Two physical applications of the non-gaussian effects have been considered. The first one, the -Doppler broadening of spectral lines from an excited gas is obtained from analytical expressions. The second one, a mathematical relationship between the entropic index and the stellar polytropic index is shown by using the thermodynamic formulation for self-gravitational systems / Considerando um g?s ideal n?o relativ?stico, os fundamentos da teoria cin?tica padr?o s?o investigados no contexto da mec?nica estat?stica n?o-gaussiana introduzida por Kaniadakis. O novo formalismo ? baseado na generaliza??o do teorema-H de Boltzmann e na dedu??o de Maxwell da distribui??o estat?stica. A distribui??o lei de pot?ncia calculada ? parametrizada por um par?metro medindo o grau de n?o-gaussianidade do sistema. No limite = 0, a teoria gaussiana de Maxwell-Boltzmann ? recuperada. Duas aplica??es dos efeitos n?o-gaussiano s?o estudados. Na primeira, o -alargamento Doppler das linhas espectrais de um g?s excitado ? obtido a partir das express?es anal?ticas. Na segunda, uma rela??o matem?tica entre o ?ndice entr?pico e o ?ndice politr?pico estelar ? mostrada usando uma formula??o termodin?mica para sistemas autogravitantes

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