QUARK AND GLUON CONDENSATES IN NUCLEAR-MATTER

Quark and gluon condensates in nuclear matter are studied. These in-medium condensates may be linked to a wide range of nuclear phenomena and are important inputs to QCD sum-rule calculations at finite density. The Hellmann-Feynman theorem yields a prediction of the quark condensate that is model independent to first order in the nucleon density. This linear density dependence, with slope determined by the nucleon sigma term, implies that the quark condensate is reduced considerably at nuclear matter saturation density-it is roughly 25-50% smaller than the vacuum value. The trace anomaly and the Hellmann-Feynman theorem lead to a prediction of the gluon condensate that is model independent to first order in the nucleon density. At nuclear matter saturation density, the gluon condensate is about 5% smaller than the vacuum value. Contributions to the in-medium quark condensate that are of higher order in the nucleon density are estimated with mean-field quark-matter calculations using the Nambu-Jona-Lasinio and Gell-Mann-Levy models. Treatments of nuclear matter based on hadronic degrees of freedom are also considered, and the uncertainties are discussed.