Holographic Duals of Long Open Strings

TL;DR

This paper explores the holographic correspondence between long open strings in string theory and boundary operators, focusing on a generalized holographic QCD model that incorporates chiral symmetry breaking and meson spectrum modifications.

Contribution

It introduces a top-down holographic QCD model with both spontaneous and explicit chiral symmetry breaking via long open strings, extending previous models and analyzing their effects on meson spectra.

Findings

First top-down holographic model with combined chiral symmetry breaking.

Semi-classical string worldsheets dominate operator expectation values.

Deformation affects meson spectrum and mimics quark mass effects.

Abstract

We study the holographic map between long open strings, which stretch between D-branes separated in the bulk space-time, and operators in the dual boundary theory. We focus on a generalization of the Sakai-Sugimoto holographic model of QCD, where the simplest chiral condensate involves an operator of this type. Its expectation value is dominated by a semi-classical string worldsheet, as for Wilson loops. We also discuss the deformation of the model by this operator, and in particular its effect on the meson spectrum. This deformation can be thought of as a generalization of a quark mass term to strong coupling. It leads to the first top-down holographic model of QCD with a non-Abelian chiral symmetry which is both spontaneously and explicitly broken, as in QCD. Other examples we study include half-supersymmetric open Wilson lines, and systems of D-branes ending on NS5-branes, which can be analyzed using worldsheet methods.