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Critical Study of the Static Functional Integral Method in the Hubbard Model
Author(s) -
Lorenz B.,
Fehske H.
Publication year - 1984
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221260128
Subject(s) - hubbard model , integral equation , functional integration , representation (politics) , physics , field (mathematics) , moment (physics) , density functional theory , statistical physics , quantum electrodynamics , mathematics , condensed matter physics , quantum mechanics , mathematical analysis , pure mathematics , superconductivity , politics , political science , law
Abstract The effect of the static approximation in the functional integral representation of the paramagnetic Hubbard model is critically investigated. The exactly solvable two‐site model is treated within the one‐ and two‐field static functional integral method and some thermodynamic properties (local magnetic moment, specific heat c v ) are compared with the exact solution for various interaction strengths and electron densities. It is shown that the static functional integral theory yields unphysical results for c v in the strong interacting system at small densities. The two‐field and one‐field methods are preferable in the low‐ and high‐temperature regions, respectively.