Dynamics of Flux Tubes in Large N Gauge Theories

TL;DR

This paper investigates the behavior and stability of flux tube excitations in large N gauge theories using AdS/CFT, revealing a coupling-dependent spectrum and matching weak and strong coupling results.

Contribution

It demonstrates the presence of flux tube excitations only above a critical coupling and compares their density of states at weak and strong coupling regimes.

Findings

Flux tube excitations exist only above a certain critical coupling.

The density of states at strong coupling matches ladder diagram models at weak coupling.

Correlation functions at large distances agree with AdS/CFT predictions rather than weakly coupled gauge theories.

Abstract

The gluonic field created by a static quark anti-quark pair is described via the AdS/CFT correspondence by a string connecting the pair which is located on the boundary of AdS. Thus the gluonic field in a strongly coupled large N CFT has a stringy spectrum of excitations. We trace the stability of these excitations to a combination of large N suppressions and energy conservation. Comparison of the physics of the N=infinity flux tube in the {\cal N}=4 SYM theory at weak and strong coupling shows that the excitations are present only above a certain critical coupling. The density of states of a highly excited string with a fold reaching towards the horizon of AdS is in exact agreement at strong coupling with that of the near-threshold states found in a ladder diagram model of the weak-strong coupling transition. We also study large distance correlations of local operators with a Wilson loop, and show that the fall off at weak coupling and N=infinity (i.e. strictly planar diagrams) matches the strong coupling predictions given by the AdS/CFT correspondence, rather than those of a weakly coupled U(1) gauge theory.