Condition for gapless color-antitriplet excitations in NJL models

Abstract

We present an exact condition for the existence of gapless quasiparticle excitations in NJL models of color superconducting quark matter with a quark-quark interaction in the scalar color-antitriplet channel. The condition can be represented by a rotated ellipse in the plane of mass and chemical potential differences for the paired quark fields.

Comments: Accepted for publication in PRC. 5 pages, 4 figures; Corrected typos and added one more term to the series expansion in (19)