NGN, QCD_2 and chiral phase transition from string theory

TL;DR

This paper constructs a string theory model involving D2-D8-$ar{D8}$ branes to study chiral phase transitions and low-energy dynamics, revealing different behaviors at weak and strong coupling and analyzing the associated holographic duals.

Contribution

It introduces a novel D2-D8-$ar{D8}$ brane setup to explore chiral symmetry breaking and phase transitions in a two-dimensional field theory from string theory.

Findings

Weak coupling: nonlocal Gross-Neveu model with chiral symmetry breaking.

Strong coupling: holographic dual description of the system.

Finite temperature: phase transition of chiral symmetry breaking.

Abstract

We construct a D2-D8-$\bar{D8}$ configuration in string theory, it can be described at low energy by two dimensional field theory. In the weak coupling region, the low energy theory is a nonlocal generalization of Gross-Neveu(GN) model which dynamically breaks the chiral flavor symmetry $U(N_f)_L \times U(N_f)_R$ at large $N_c$ and finite $N_f$. However, in the strong coupling region, we can use the SUGRA/Born-Infeld approximation to describe the low energy dynamics of the system. Also, we analyze the low energy dynamics about the configuration of wrapping the one direction of D2 brane on a circle with anti-periodic boundary condition of fermions. The fermions and scalars on D2 branes get mass and decouple from the low energy theory. The IR dynamics is described by the $QCD_2$ at weak coupling. In the opposite region, the dynamics has a holographic dual description. And we have discussed the phase transition of chiral symmetry breaking at finite temperature. Finally, after performing T-duality, this configuration is related to some other brane configurations.