RG-Consistent (P)NJL Model: Impact of Thermal Cutoff Modifications on Thermodynamics and Net-Baryon Number Fluctuations

TL;DR

This study explores how renormalization group consistency and a temperature-dependent thermal cutoff influence thermodynamics and net-baryon fluctuations in QCD models, improving agreement with lattice data.

Contribution

It introduces a thermal cutoff modification in RG-improved NJL models, enhancing thermodynamic convergence and fluctuation predictions compared to previous approaches.

Findings

RG consistency ensures thermodynamic quantities approach Stefan-Boltzmann limit at high T.

RGPNJL model shows non-monotonic sensitivity to the cutoff parameter k.

Enhanced description of net-baryon fluctuations aligns better with lattice QCD data.

Abstract

In this paper, we investigate the impact of renormalization group (RG) consistency on the chiral phase transition and thermodynamic properties of QCD matter using the RGNJL and RGPNJL models. By implementing a temperature-dependent thermal cutoff $\Lambda_T = k\Lambda_0$, we ensure that thermodynamic quantities converge toward the Stefan-Boltzmann limit at high temperatures, effectively extending the applicability of these effective theories. Our analysis shows that while the RG-consistency condition ($k \rightarrow \infty$) resolves causality violations in the RGNJL model by binding the speed of sound to the conformal limit, the RGPNJL model exhibits a more complex, non-monotonic sensitivity to the parameter $k$. Furthermore, we demonstrate that the RG-improved PNJL framework significantly enhances the description of net-baryon number fluctuations ($\kappa\sigma^2$) relative to lattice QCD data at vanishing chemical potential, though the intensification of these fluctuations at high baryon density highlights a critical sensitivity to the model's parametric constraints. This study provides a rigorous evaluation of the RG-consistency framework's predictive power in mapping the QCD phase diagram and interpreting experimental observables.