Critical Enhancement of the In-medium Nucleon-Nucleon Cross Section at   low Temperatures
  The in-medium nucleon-nucleon cross section is calculated starting from the thermodynamic T-matrix at finite temperatures. The corresponding Bethe-Salpeter-equation is solved using a separable representation of the Paris nucleon-nucleon-potential. The energy-dependent in-medium N-N cross section at a given density shows a strong temperature dependence. Especially at low temperatures and low total momenta, the in-medium cross section is strongly modified by in-medium effects. In particular, with decreasing temperature an enhancement near the Fermi energy is observed. This enhancement can be discussed as a precursor of the superfluid phase transition in nuclear matter. 
T. Alm(1), G. Roepke(1) and M. Schmidt(2) ((1)Arbeitsgruppe der   Max-Planck-Gesellschaft ``Theoretische Vielteilchenphysik ...