Sakai-Sugimoto model, Tachyon Condensation and Chiral symmetry Breaking

TL;DR

This paper extends the Sakai-Sugimoto model by incorporating the open string tachyon, linking tachyon condensation with chiral symmetry breaking, and providing a more consistent holographic description of QCD-like phenomena.

Contribution

The authors introduce a modified Sakai-Sugimoto model including the tachyon, establishing a classical solution where chiral symmetry breaking aligns with tachyon condensation.

Findings

Tachyon condensation triggers chiral symmetry breaking.

The model identifies parameters for quark mass and chiral condensate.

Brief discussion of mesonic spectra in the modified model.

Abstract

We modify the Sakai-Sugimoto model of chiral symmetry breaking to take into account the open string tachyon which stretches between the flavour D8-branes and anti D8-branes. There are several reasons of consistency for doing this: (i) Even if it might be reasonable to ignore the tachyon in the ultraviolet where the flavour branes and antibranes are well separated and the tachyon is small, it is likely to condense and acquire large values in the infrared where the branes meet. This takes the system far away from the perturbatively stable minimum of the Sakai-Sugimoto model; (ii) The bifundamental coupling of the tachyon to fermions of opposite chirality makes it a suitable candidate for the quark mass and chiral condensate parameters. We show that the modified Sakai-Sugimoto model with the tachyon present has a classical solution satisfying all the desired consistency properties. In this solution chiral symmetry breaking coincides with tachyon condensation. We identify the parameters corresponding to the quark mass and the chiral condensate and also briefly discuss the mesonic spectra.