We propose several quark mass deformations of the holographic model of massless QCD using the D4/D8/-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 is 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.
ASJC Scopus subject areas
- Nuclear and High Energy Physics