Two-flavor color superconductivity in a general Nambu-Jona-Lasinio model with color and charge neutrality

TL;DR

This paper investigates the role of various interaction channels in charge-neutral two-flavor color-superconducting quark matter using a comprehensive NJL model, revealing the importance of multiple channels and the existence of a gapless phase.

Contribution

It introduces a detailed analysis of interaction channels in a generalized NJL model under neutrality constraints, identifying key channels affecting the phase structure.

Findings

Scalar-isovector, vector-isovector, and vector-isovector-color-octet channels are significant.

A gapless two-flavor color-superconducting phase exists between normal and gapped phases.

Phase diagrams depend critically on the dominant interaction channels.

Abstract

By using a general NJL model including as many interaction channels as possible, and taking into account the constraints imposed by color and charge neutrality, we analyze how the different interaction channels contribute to the charge-neutral two-flavor color-superconducting matter. After taking the Fierz transformation, the number of parameters in the NJL model is reduced and thereby quark-antiquark condensates and diquark condensates are related. Through a self-consistent solution of the gap equations, we find that in addition to the diquark and vector channels, the scalar-isovector, vector-isovector, and vector-isovector-color-octet channels are also important, while other channels can be neglected. Moreover, between the normal quark matter phase and two-flavor color-superconducting phase, there is a gapless two-flavor color-superconducting phase. The fractions of quarks with different flavors and colors are calculated in both gaped and gapless two-flavor color-superconducting phases. In addition, We illustrate the phase diagrams in the diquark coupling and chemical potential plane, and discuss in detail how the dominant channels influence these phase diagrams.