2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/97978The one-dimensional t-J model with density-density repulsive interactions is investigated using exact diagonalization and quantum Monte Carlo methods. A short-range repulsion pushes phase separation to larger values of J/t, and leads to a widened precursor region in which a spin gap and strengthened superconducting correlations appear. The correlation exponent is calculated. On the contrary, a long-range repulsion of $1/r$-form suppresses superconductivity in the precursor region.26 pages (RevTeX), 10 figures available upon request as PostScript file or hardcopy, IPS-Report Nr. 93/01Condensed Mattertext