2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/148700We study the singularities in X-ray absorption spectra of one-dimensional Hubbard and $t$--$J$ models. We use Boundary Conformal Field Theory and the Bethe Ansatz solutions of these models with both periodic and open boundary conditions to calculate the exponents describing the power-law decay near the edges of X-ray absorption spectra in the case where the core-hole potential has bound states.16 pages of revtex, 8 figures, some typos corrected, references addedStrongly Correlated Electronstext