Clusters and condensates in Fermi systems
  Superconductivity, superfluidity, condensation, cluster formation, etc. are phenomena that might occur in many-particle systems. These are due to residual interactions between the particles. To explain these phenomena consistently in a microscopic approach, at some point, one needs to solve few-body equations that are modified because of the Pauli principle and the interactions of the many particles around. 
Michael Beyer (U Rostock)