Evaluation of the pi pi-scattering amplitude in the sigma-channel at finite density

The pi pi scattering amplitude in the sigma-channel is studied at finite baryonic density in the framework of a chiral unitary approach which successfully reproduces the meson meson phase shifts and generates the f(0) and sigma resonances in vacuum. We address here a new variety of mechanisms recently suggested to modify the pi pi interaction in the medium, as well as the role of the s-wave selfenergy, in addition to the p-wave, in the dressing of the pion propagators