2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/198951We derive in-medium PROTON-PROTON cross sections in a microscopic model based upon the Bonn nucleon-nucleon potential and the Dirac-Brueckner approach for nuclear matter. We demonstrate the difference between proton-proton and neutron-proton cross sections and point out the need to distinguish carefully between the two cases. We also find substantial differences between our in-medium cross sections and phenomenological parametrizations that are commonly used in heavy-ion reactions.9 pages of RevTex and 4 figures (postscript in separate uuencoded file), UI-NTH-9309Nuclear Theorytext