Hairpin-Branes and Tachyon-Paperclips in Holographic Backgrounds

TL;DR

This paper introduces an improved effective field theory for D-branes with U-shaped geometries in holographic backgrounds, emphasizing the importance of a light complex scalar mode and demonstrating its effectiveness in specific string theory contexts.

Contribution

It develops an abelian tachyon-DBI action that captures the non-local physics of the scalar mode, surpassing the traditional DBI approach for certain holographic branes.

Findings

The tachyon-DBI action effectively describes hairpin-branes in NS5-brane backgrounds.

It provides insights into chiral symmetry breaking and quark mass in holographic QCD.

The approach models open string tachyon condensation in curved spaces.

Abstract

D-branes with a U-shaped geometry, like the D8 flavor branes in the Sakai-Sugimoto model of QCD, are encountered frequently in holographic backgrounds. We argue that the commonly used DBI action is inadequate as an effective field theory description of these branes, because it misses a crucial component of the low-energy dynamics: a light complex scalar mode. Following an idea of Erkal, Kutasov and Lunin we elaborate on an effective description based on the abelian tachyon-DBI action which incorporates naturally the non-local physics of the complex scalar mode. We demonstrate its power in a context where an explicit worldsheet description of the open string dynamics exists --hairpin-branes in the background of NS5-branes. Our results are relevant for the holographic description of chiral symmetry breaking and bare quark mass in QCD and open string tachyon condensation in curved backgrounds.