Quark condensate at finite baryon density.

Abstract

We discuss a recently derived, model-independent relation that expresses the value of a medium-modified quark condensate in terms of the vacuum value of the condensate and the value of the nucleon sigma term, [sigma][sub [ital N]]. Our goal is to calculate the value of the quark condensate in nuclear matter, [l angle]NM[vert bar][ital [bar q]](0)[ital q](0)[vert bar]NM[r angle], using some standard many-body techniques. Here, we comment on the mean-field calculations of Cohen, Furnstahl, and Griegel and others. We then calculate the value of the nuclear matter quark condensate using linear response theory. In a sigma-dominance model, the linear response calculation relates the modification of the vacuum condensate to the matrix element of the operator [ital [bar q]q] taken between a state of the sigma meson and the vacuum. (That matrix element may be used to define a sigma decay constant, [ital f][sub [sigma]].) We also provide some additional insight into the relation between the dynamics of the quark condensate and the scalar fields of relativistic nuclear physics.