Effects of a multi-quark interaction on color superconducting phase transition in an extended NJL model

TL;DR

This paper investigates how a multi-quark interaction influences the phase transitions between chiral symmetry breaking and color superconductivity within an extended NJL model, revealing conditions for coexistence or separation of phases.

Contribution

It introduces a nonlinear chiral-diquark coupling in the NJL model and analyzes its effects on phase coexistence and transition behavior.

Findings

Coexistence phase depends on the sign of the nonlinear coupling.

Large coexistence region aligns with the quark-diquark nucleon model.

Small coexistence region supports Ginzburg-Landau applicability.

Abstract

We study the interplay of the chiral and the color superconducting phase transitions in an extended Nambu--Jona-Lasinio model with a multi-quark interaction that produces the nonlinear chiral-diquark coupling. We observe that this nonlinear coupling adds up coherently with the \omega^2 interaction to produce the chiral-color superconductivity coexistence phase or cancel each other depending on its sign. We discuss that large coexistence region in the phase diagram is consistent with the quark-diquark picture for the nucleon whereas its smallness is the prerequisite for the applicability of the Ginzburg-Landau approach.