Quark Mass Deformation of Holographic Massless QCD

TL;DR

This paper introduces quark mass deformations in a holographic QCD model by adding D-branes, leading to mass generation via worldsheet instantons and deriving key relations like Gell-Mann-Oakes-Renner.

Contribution

It presents a novel method to incorporate quark masses into the holographic QCD model using D-brane deformations, extending the Sakai-Sugimoto framework.

Findings

Quark and pion masses generated by worldsheet instantons.

Derived the Gell-Mann-Oakes-Renner relation.

Calculated the chiral condensate value.

Abstract

We propose several quark mass deformations of the holographic model of massless QCD using the D4/D8/D8bar brane configuration proposed by Sakai and Sugimoto. The deformations are based on introducing additional D4 or D6 branes away from the QCD D4 branes. The idea is similar to extended technicolor theories, where the chiral symmetry breaking by additional D-branes are mediated to QCD to induce non-zero quark masses. In the D-brane picture as well as the holographic dual gravity description, the quark and the pion masses are generated by novel worldsheet instantons with finite area. We also derive the Gell-Mann-Oakes-Renner relation, and find the value of the chiral condensate in the Sakai-Sugimoto model.