Stringy NJL and Gross-Neveu models at finite density and temperature

TL;DR

The paper investigates the finite-temperature and finite-density phase structure of nonlocal stringy NJL and Gross-Neveu models using probe D-branes in the near-horizon geometry of D4-branes. By contrasting strong-coupling gravity results (straight vs curved branes, with or without fundamental strings) with the corresponding large-$N$ field theory NJL/GN analyses, it highlights qualitative agreements at low temperatures and systematic differences at high temperatures, notably the order of phase transitions. A key methodological advance is the construction of off-shell Landau potentials by deforming the probe-brane profiles, enabling a unified view of stable, metastable, and mixed phases in both models. The work also clarifies how the stringy models reproduce the bosonization structure of GN and how chiral symmetry breaking manifests holographically, offering a framework to glean insights into dense QCD-like dynamics from holographic setups.

Abstract

Nonlocal stringy versions of the Nambu-Jona-Lasinio and Gross-Neveu models arise in a certain limit of holographic QCD. We analyze the phase structure at finite density and temperature at strong coupling in terms of probe branes in the gravity dual. Comparison with the phase structure of the local field theory models shows qualitative agreement with some aspects, and disagreement with others. Finally, we explain how to construct the Landau potentials for these models by taking the probe branes off-shell.