Coherent Potential Approximation
Mostrando 1-7 de 7 artigos, teses e dissertações.
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1. Gas de Bose diluido fracamente confinado / Dilute Bose gas weakly confined
A critical study of atomic Bose-Einstein condensates (BECs) is presented. Taking as a starting point the physics of the free gas, we study the effect of weakly confining potentials. Two cases were studied in detail: i) an atomic gas in a finite square well potential with a few bound states; and ii) a system confined in two-dimensions by an isotropic harmonic
Publicado em: 2010
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2. ESTUDO DO PARÂMETRO DE ORDEM E DO MOMENTO MAGNÉTICO EM BOROCARBETOS PSEUDOQUATERNÁRIOS / STUDY OF ORDER PARAMETER AND MAGNETIC MOMENT IN PSEUDOQUATERNARY BOROCARBIDES
Experimental data show that the dissolved impurities of the Mn presents a magnetic moment when substitute the Ni atom in pseudoquaternary borocarbide Y (Ni(1−x)Mx)2B2C, this is not observed if the impurities are Fe and Co. In this work we do a theoretical study of the superconducting order parameter variation and a possible formation of impurities magn
Publicado em: 2007
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3. Theoretical calculus of magnetocaloric effects of La(FexSi1-x)13. / Cálculo teórico do efeito magnetocalórico do composto La(FexSi1-x)13.
The study of the magnetocaloric effect of the compound La(FexSi1-x)13 became very important, once recent experiments revealed that this compound exhibits great values of the isothermal entropy change (Δ S) and the adiabatic temperature change(ΔTad), which are the quantities used to characterize the power of refrigeration of any compound. We studied
Publicado em: 2006
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4. Semiclassical propagation of coherent states / Propagação semiclassica de estados coerentes
This thesis addresses di®erent aspects of the semiclassical propagation of coherent states. We have derived a general expression for the propagator connecting these states which, di®erently from previous formulae in the literature, is valid for packets of arbitrary widths. The result, obtained via functional integration, depends on classical trajectories i
Publicado em: 2005
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5. Modelo de Anderson para duas impurezas : Metodo dos campos efetivos / The two-impurity Anderson model : an effective medium approach
O Hamiltoniano do modelo de Anderson para duas impurezas é estudado via um desacoplamento das funções de Green. Neste caso resulta ser equivalente a aproximação de potencial coerente (CPA) que também, neste caso, coincide com a aproximação Hubbard-I. Consideram-se todos os termos de interação impureza-impureza, tanto os denominados termos de um cor
Publicado em: 2004
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6. Ordem e caos em plasmas magnetizados
The objective of this thesis is to present a clear understanding of some important nonlinear phenomena that are common in space and laboratory plasmas. Specifically,the present analytical and numerical studies have focused on the properties of electromagnetic turbulence as well as associated coherent structures and chaotic behaviors in a multi-component magn
Publicado em: 1999
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7. Estudos semiclassicos na representação de estados coerentes
In this work we develop and apply a semiclassical approximation to the coherent-state propagator K(z",z ,t) = (z"iHt/h)z ), where H is the Hamilton operator for the suystem and z) represents the coherent states of the harmonic oscilator. The semiclassical K(z",z ,t) makes use of a stationary phase approxiamtion in which stationary trajectories inhabit is stu
Publicado em: 1997