Medium modification of two-particle scattering in nonideal Bose systems

Medium modification of scattering properties in interacting Bose systems are considered by solving the Bethe-Salpeter equation. An equation of state for the normal phase (generalized Beth-Uhlenbeck formula) is given using the in-medium phase shifts to include two-particle correlations. Conclusions are drawn for systems of bosonic atoms with repulsive interaction such as sodium (Na-23) and rubidium (Rb-87). It is shown that the negative slope of the in-medium phase shift at zero momentum and the absolute value of the in-medium scattering phase shift for low scattering energies increase with density.