Impact of Four-Quark Condensates on In-Medium Effects of Hadrons
  Spectral properties of hadrons in nuclear matter are treated in the framework of QCD sum rules. The influence of the ambient strongly interacting medium is encoded in various condensates. Especially, the structure of different four-quark condensates and their density dependencies in light quark systems are exemplified for the omega meson and the nucleon. 
R. Thomas, T. Hilger, S. Zschocke, B. Kampfer