Browsing Exact and Earth Sciences by Subject "Metodos de funcoes de green"

Now showing items 1-6 of 6

    • Approximate Treatment of a Two-Dimensional Anisotropic Peierls-Hubbard Model 

      Bernhard, Ben Hur; Iglesias, Jose Roberto (1993) [Journal article]
      A Green-function formalism is presented to study a Peierls-Hubbard Hamiltonian in two dimensions. The 1attice consists of parallel dimerized chains with alternating nearest-neighbor hoppings t and t 11 and another hopping ...

    • Cumulant expansion of the periodic Anderson model : general derivation 

      Figueira, M.S.; Foglio, M.E.; Martinez Pino, Gerardo Guido (1994) [Journal article]
      We extend to the periodic Anderson model (PAM) the diagrammatic expansion in cumulants that was employed by Hubbard to study his model of a narrow band of strongly correlated electrons. The PAM is a lattice of localized ...

    • From the atomic limit to a metal-insulator transition in the hubbard model 

      Craco, Luis; Gusmao, Miguel Angelo Cavalheiro (1995) [Journal article]
      Starting from the exact solution of the Hubbard model in the atomic limit, and treating the hopping term as a perturbation by means of a diagram technique, we discuss the electronic structure of the model in some simple ...

    • Green-Function Method for a Mixed-Valence Hamiltonian 

      Simões, Acirete Souza da Rosa; Iglesias, Jose Roberto; Anda, Enrique V. (1984) [Journal article]
      A Green-function diagrammatic method is utilized to calculate the occupation number of a narrow (j) band in a mixed-valence system. The method is a generalization of the Hubbard-1 approximation for a two-band Hamiltonian. ...

    • Magnetic susceptibility and specific heat of the anderson lattice : perturbative expansion around the atomic limit 

      Brunnet, Leonardo Gregory; Gusmao, Miguel Angelo Cavalheiro; Iglesias, Jose Roberto (1992) [Journal article]
      The Green's functions relevant to the periodic Anderson Hamiltonian are calculated via perturbation theory around the atomic limit. The approximation reproduces exact results in three different limits: zero bandwidth, zero ...

    • Saturating field configurations for the massless thirring-wess model 

      Girotti, Horacio Oscar (1979) [Journal article]
      The saturation of the massless Thirring-Wess model by induced field configurations is presented. The limiting procedure connecting the massless Thirring-Wess model arith the Schwinger model is reexamined. Special emphasis ...