Renormalization group approach to the interacting boson fermion systems
  We study a pseudogap region of the mixed boson fermion system using a recent formulation of the renormalization group technique through the set of infinitesimal unitary transformations. Renormalization of fermion energies gives rise to a depletion of the low energy states (pseudogap) for temperatures $T^{*}>T>T_{c}$ which foreshadows appearance of the pairwise correlations with their long range phase coherence being missed. With a help of the flow equations for boson and fermion operators we analyze spectral weights and finite life times of these quasiparticles caused by interactions. 
T. Domanski (UMCS Lublin, Poland), J. Ranninger (CNRS Grenoble,   France)