Asymptotic Freedom in Holographic QCD

TL;DR

This paper investigates the behavior of quark mass and condensate in a holographic QCD model, demonstrating how the sign of the dilaton field affects physical predictions and matching known QCD features.

Contribution

It shows that the dynamical soft-wall model can correctly reproduce the running of quark parameters with proper dilaton sign and spectrum, improving upon previous models.

Findings

Correct quark running obtained with proper dilaton sign

Absence of unphysical massless vector mesons with right parameters

Model allows non-zero quark condensate in chiral limit

Abstract

We calculate the running of the quark mass and the quark condensate using a dynamical soft-wall model by Csaki and Reece. We show that a correct running can be obtained with an appropriate sign for the dilaton field. In the soft-wall model with quadratic dilaton profile, a wrong sign for the dilaton field can give rise to a massless vector meson, a signature of spontaneously broken symmetry in the vector sector, which is not observed in nature. With a right parameter range, we obtain no such massless vector meson. We also find that, contrary to the soft-wall model with quadratic dilaton profile, the model allows a non-vanishing quark condensate in the chiral limit. We obtain the vector meson mass spectrum similar to that of the hard-wall model. By varying a parameter in the model we can fit the running of the quark mass and of the quark condensate.