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17 records were found.

## Effective t-J Hamiltonian for the Copper Oxides

Comment: (ps version of the dvi file, resubmitted because previous uucompressed version was corrupted), 9 pages

## Self-consistent calculation of particle-hole diagrams on the Matsubara frequency: FLEX approximation

Comment: seven pages, nine figures as ps files. Accepted in Int. J. Modern Phys. C (1997)

## Metal-Insulator Transition in the Two-Dimensional Hubbard Model at Half-Filling with Lifetime Effects within the Moment Approach

We explore the effect of the imaginary part of the self-energy, $Im\Sigma(\vec{k},\omega)$, having a single pole, $\Omega(\vec{k},\omega)$, with spectral weight, $\alpha(\vec{k})$, and quasi-particle lifetime, $\Gamma(\vec{k})$, on the density of states. We solve the set of parameters, $\Omega(\vec{k},\omega$), $\alpha(\vec{k})$, and $\Gamma(\vec{k})$ by means of the moment approach (exact sum rules) of Nolting. Our choice for $\Sigma(k,\omega)$, satisfies the Kramers - Kronig relationship automatically. Due to our choice of the self - energy, the system is not a Fermi liquid for any value of the interaction, a result which is also true in the moment approach of Nolting without lifetime effects. By increasing the value of the local interaction, $U/W$, at half-filling ($\rho = 1/2$), we go from a paramagnetic metal to a paramagnetic i...

## Superconductivity in the Attractive Hubbard Model: The Double Hubbard--I Approximation

Comment: 6 pages, revtex, to be published in Helvetica Physica Acta

## Evolution of One-Particle and Double-Occupied Green Functions for the Hubbard Model at Half-Filling With Lifetime Effects Within The Moment Approach

Comment: 08 pages, 12 figures ps, revtex, submitted to Phys. Rev. B

## Comment on Superconducting phases in the presence of Coulomb interaction: From weak to strong correlations''

Comment: 2 pages. 1 figure in .ps

## s-wave superconductivity in the presence of local Coulomb correlations

We derive the superconductiong mean-field equations for an attractive interaction, V, in the s-wave channel when local Coulomb interactions are taken into account for any value of U. Our results show that the Coulomb repulsion is detrimental to the critical temperature, $T_c$, and the order parameter, $\Delta(T)$, for values of $U \geq |V|$. Furthermore, our results depend on band filling in a sensible way. In the presence of local correlations, $2\Delta(0)/T_c$ differs from the BCS ratio, since Coulomb interactions affect much more the superconducting critical temperature, $T_c$, than the superconducting order parameter, $\Delta(T)$. We conclude that the presence of Coulomb interactions play an additional role in the analysis of experimental data, specially in narrow band systems.

## Ginzburg-Landau Expansion in Non-Fermi Liquid Superconductors: Effect of the Mass Renormalization Factor

Comment: accepted for publication in Physical Review B

## Evidence for a metallic--like state in the T=0 K phase diagram of a high temperature superconductor

Comment: 5 pages, accepted for publication in European Physical Journal B

## Moment Approach for the 2D Attractive Hubbard Model

Comment: 8 pages, 3 figures (2 ps files for Fig. 2) To appear in Physica A