Quark Mass Deformation of Holographic Massless QCD

Understand

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.