Phenomenological study of the anisotropic quark matter in the 2-flavor Nambu-Jona-Lasinio model

TL;DR

This study explores how momentum anisotropy affects the phase structure, mesonic properties, and transport coefficients in quark matter modeled by the 2-flavor NJL model, revealing significant shifts in critical points and transport behaviors.

Contribution

It introduces a phenomenological analysis of anisotropic quark matter within the NJL model, highlighting the impact of anisotropy on phase transitions, meson properties, and transport coefficients.

Findings

Anisotropy catalyzes chiral symmetry breaking.

Critical endpoint shifts to lower temperatures and higher chemical potentials with increased anisotropy.

Transport coefficients like shear viscosity and electrical conductivity are affected by anisotropy, showing shifted minima.

Abstract

With the two flavor Nambu-Jona-Lasinio (NJL) model we carry out a phenomenological study on the chiral phase structure, mesonic properties and transport properties in a momentum-space anisotropic quark matter. To calculate transport coefficients we have utilized the kinetic theory in the relaxation time approximation, where the momentum anisotropy is embedded in the estimation of both distribution function and the relaxation time. It is shown that an increase of the anisotropy parameter $\xi$ may results in a catalysis of chiral symmetry breaking. The critical endpoint (CEP) is shifted to smaller temperatures and larger quark chemical potentials as $\xi $ increases, the impact of momentum anisotropy on temperature of CEP is almost the same as that on the quark chemical potential of CEP. The meson masses and the associated decay widths also exhibit a significant $\xi$ dependence. It is observed that the temperature behavior of scaled shear viscosity $\eta/T^3$ and scaled electrical conductivity $\sigma_{el}/T$ exhibit a similar dip structure, with the minima of both $\eta/T^3$ and $\sigma_{el}/T$ shifting toward higher temperatures with increasing $\xi$. Furthermore, we demonstrate that the Seebeck coefficient $S$ decreases when temperature goes up and its sign is positive, indicating the dominant carriers for converting the temperature gradient to the electric field are up-quarks. The Seebeck coefficient $S$ is significantly enhanced with a large $\xi$ for the temperature below the critical temperature.