ANISOTROPIC SUPERCONDUCTIVITY IN THE 2-DIMENSIONAL HUBBARD-MODEL

We address the problem of relative stability of the d-wave and extende d s-wave superconductivity in the two-dimensional Hubbard model. The C oulomb correlations are taken into account in the two-pole version of the mean-field-like approximation for the auxiliary boson fields. The d-wave superconductivity is more likely to occur for small hole concen trations but for some particular region of parameters the competition between two types of symmetry and cross-over behavior is possible. We discuss the relevance of our model calculations to the theory of high- temperature superconductors.