Exploring improved holographic theories for QCD: Part I

TL;DR

This paper explores five-dimensional holographic models for QCD, proposing a gravity-dilaton-axion framework that captures key features like confinement and asymptotic freedom, with results on vacuum structure and glueball spectra.

Contribution

It introduces a holographic QCD model with a dilaton potential linked to the QCD beta-function, providing a new approach to analyze confinement and spectrum calculations.

Findings

The dilaton potential corresponds exactly to the QCD beta-function.

The model exhibits confining backgrounds with IR singularities suitable for spectrum analysis.

Asymptotically linear glueball masses are achievable within this framework.

Abstract

Various holographic approaches to QCD in five dimensions are explored using input both from the putative non-critical string theory as well as QCD. It is argued that a gravity theory in five dimensions coupled to a dilaton and an axion may capture the important qualitative features of pure QCD. A part of the higher alpha' corrections are resummed into a dilaton potential. The potential is shown to be in one-to-one correspondence with the exact beta-function of QCD, and its knowledge determines the full structure of the vacuum solution. The geometry near the UV boundary is that of AdS_5 with logarithmic corrections reflecting the asymptotic freedom of QCD. We find that all relevant confining backgrounds have an IR singularity of the "good" kind that allows unambiguous spectrum computations. Near the singularity the 't Hooft coupling is driven to infinity. Asymptotically linear glueball masses can also be achieved. The classification of all confining asymptotics, the associated glueball spectra and meson dynamics are addressed in a companion paper, ArXiv:0707.1349