We 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.Comment: 9 pages of RevTex and 4 figures (postscript in separate uuencoded
file), UI-NTH-930