Chiral crystal in cold QCD matter at intermediate densities? art. no. 034008

The analogue of Overhauser (particle-hole) pairing in electronic systems (spin-density waves with non-zero total momentum Q) is analyzed in finite-density QCD for 3 colors and 2 flavors, and compared to the color-superconducting BCS ground state (particle-particle pairing, Q = 0). The calculations are based on effective nonperturbative four-fermion interactions acting in both the scalar diquark as well as the scalar-isoscalar quark-hole ("sigma") channel. Within the Nambu-Gorkov formalism we set up the coupled channel problem, including multiple chiral density wave formation, and evaluate the resulting gaps and free energies. Employing medium-modified instanton-induced 't Hooft interactions, as applicable around mu (q) similar or equal to 0.4 GeV (or 4 times nuclear saturation density), we find the "chiral crystal phase" to be competitive with the color super conductor.