Non critical holographic models of the thermal phases of QCD

TL;DR

This paper investigates the thermal phases of a non-critical holographic QCD model, revealing phase transitions, meson spectra, and quark drag properties, with results similar to the Sakai-Sugimoto model.

Contribution

It introduces a non-critical holographic model of QCD with detailed phase diagram analysis and meson spectrum characterization, extending understanding of thermal QCD phases.

Findings

Low-temperature confining phase with broken chiral symmetry

High-temperature deconfining phase with chiral symmetry restoration or breaking depending on L

High-spin mesons melt above a critical angular momentum

Abstract

We analyze the thermal phases of a non critical holographic model of QCD. The model is based on a six dimensional background of $N_c$ non extremal D4 branes wrapping a spacial circle of radius $R$ and the compactified Euclidean time direction of radius $\beta=1/T$. We place in this background stacks of $N_f$ D4 and anti-D4 flavor probe branes with a separation distance $L$ at large radial direction. %The dual theory is a 4+1 dimensional $SU(N_c)$ gauge theory %compactified on a radius $R$ with anti-periodic boundary conditions for the fermions. The analysis of the DBI effective action yields the following phase diagram: At low temperature the system is in a confining phase with broken chiral symmetry. In the high temperature deconfining phase chiral symmetry can be either restored for $L>L_c=1.06 R$ or broken for $L<L_c$. All of these phase transitions are of first order. We analyze the spectrum of the low-spin and high-spin mesons. High spin mesons above certain critical angular momentum ``melt''. We detect (no) drag for (mesons) quarks moving in hot quark-gluon fluid. The results resemble the structure and properties of the thermal Sakai-Sugimoto model derived in hep-th/0604161.