Hubbard Model
Mostrando 13-24 de 26 artigos, teses e dissertações.
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13. O líquido de spin isolante no modelo de Hubbard bidimensional levemente dopado
Our main goal here is to analyze the low-energy properties of the two-dimensional (2d) Hubbard model slightly away from half-lling from a renormalization group point of view within the two-loop approximation. We will develop this technique adapting it conveniently to our problem at hand. As a warm-up test for our approach, we will apply the same methodology
Publicado em: 2006
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14. SUPERCONDUCTIVITY IN A TWO DIMENSIONAL d− p HUBBARD MODEL / SUPERCONDUTIVIDADE EM UM MODELO DE HUBBARD d− p, EM DUAS DIMENSÕES
Neste trabalho, foi usada a aproximação de dois-pólos proposta por L. Roth (Phys. Rev. 184, 451 (1969)), para investigar os efeitos da hibridização no estado normal e no estado supercondutor de um modelo de Hubbard d − p. Para tratar supercondutividade com simetria dx2−y2 , usou-se o procedimento de fatorização proposto por Beenen e Edward
Publicado em: 2006
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15. Suscetibilidades de carga e spin para uma superfície de fermi chata bidimensional
In this work we investigate the charge and spin instabilities of a two-dimensional model (d=2) of strongly interacting electrons in the presence of a at Fermi surface (FS) by using the renormalization group theory (RG). Bearing in mind the strong electronic repulsions in the cuprates superconductors, we try to relate our model to the repulsive Hubbard model
Publicado em: 2006
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16. 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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17. Introduction to quantum Monte Carlo simulations for fermionic systems
We tutorially review the determinantal Quantum Monte Carlo method for fermionic systems, using the Hubbard model as a case study. Starting with the basic ingredients of Monte Carlo simulations for classical systems, we introduce aspects such as importance sampling, sources of errors, and finite-size scaling analyses. We then set up the preliminary steps to p
Brazilian Journal of Physics. Publicado em: 2003-03
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18. MÉTODO RPA RENORMALIZADO PARA O MODELO DE HUBBARD ESTENDIDO / RENORMALIZED RPA METHOD FOR THE EXTENDED HUBBARD MODEL
In this work we apply the Random Phase Approximation (RPA) to the Extended Hubbard Model in one dimension. Initially we investigate the e®ect of the first neighbor interaction term, V , on the spin and charge susceptibilities. When V is small, its influence is also very small but as it grows, it tends to lower the plasmon frequency and to inhibit the condit
Publicado em: 2003
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19. Efeitos de temperatura e de interação finita em sistemas desordenados correlacionados
The main goal of this work is to study the role of disorder in strongly correlated systems, where the electron-electron interaction is comparable to or dominates over the electron kinetic energy. Keeping this in mind, we solve the Hubbard model and the Anderson lattice model in the presence of disorder. The main theory in which our work is based is the Dynam
Publicado em: 2003
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20. Liquidos de Luttinger não homogeneos
In this work, we study inhomogeneous strongly correlated electron systems. A Luttinger liquid superlattice, modeled by a repeated pattern of two different Luttinger liquids was considered. We find that the effective low-energy description amalgamates features of both types of liquids in proportion to their spatial extent. The Drude peak is given by the produ
Publicado em: 2001
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21. Horizontal Slug Flow in a Large-Size Pipeline: Experimentation and Modeling
The knowledge of the slug flow characteristics is very important when designing pipelines and process equipment. When the intermittences typical in slug flow occurs, the fluctuations of the flow variables bring additional concern to the designer. Focusing on this subject the present work discloses the experimental data on slug flow characteristics occurring
Journal of the Brazilian Society of Mechanical Sciences. Publicado em: 2001
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22. Expansão em cumulantes para o Modelo de Anderson Periodico
The diagrammatic expansion in cumulants that was employed by Hubbard to study his model of a narrow band of strongly correlated electrons was extended to the Periodic Anderson Model (PAM). The model was also extended by considering localized electronic states with an arbitrary scheme of energy levels: this extension would be useful to study intermediate vale
Publicado em: 1994
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23. Supercondutividade e antiferromagnetismo em um modelo de Hubbard estendido
We study an extended Hubbard model, for the one band, square lattice case. We include both, the nearest neighbor direct and correlated hopping Coulomb terms. Within a generalized Hartree-Fock scheme we obtain superconductive solutions. Those solutions may be either non magnetic or antiferromagnetic (Néel-like). A necessary condition between parameters of th
Publicado em: 1992
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24. Spinons and holons for the one-dimensional three-band Hubbard models of high-temperature superconductors.
The one-dimensional three-band Hubbard Hamiltonian is shown to be equivalent to an effective Hamiltonian that has independent spinon and holon quasiparticle excitations plus a weak coupling of the two. The spinon description includes both copper sites and oxygen hole sites leading to a one-dimensional antiferromagnet incommensurate with the copper lattice. T