Aspects of QCD Dynamics from String Theory

TL;DR

The paper studies large $N$ QCD$_4$ dynamics using supergravity on an AdS black-hole background, aiming to access strong-coupling physics such as confinement and mass gaps. It develops the QCD$_4$ dual from M5-branes via a non-extremal D4-brane background, derives the field/operator map with ${ m O}_4 o { m Tr} F^2$ and $ ilde{{ m O}}_4 o { m Tr} F ilde F$, and computes the scalar glueball spectrum, topological susceptibility, and gluon condensate as leading strong-coupling predictions. The results show qualitative (and in some cases semi-quantitative) agreement with lattice data for observables like $M_{0^{++}}$, $M_{0^{-+}}$, $ abla^2$, and $ ilde extchi_t$, while emphasizing limitations from the absence of asymptotic freedom and potential KK-mode effects. The work provides a foundational bridge between holographic descriptions and QCD-like dynamics, offering a framework to extend to full string theory and to QCD$_3$ analyses.

Abstract

We study dynamical aspects of large N QCD_4 via supergravity on Anti de Sitter black hole geometry. We compute the mass spectrum, the topological susceptibility and the gluon condensate and make a comparison to lattice simulations. We present analogous results for QCD_3.