An AdS/QCD model from tachyon condensation: II

TL;DR

This paper introduces a holographic QCD model based on tachyon condensation that captures chiral symmetry breaking, meson spectra, and temperature effects, showing improved agreement with experimental data over previous models.

Contribution

It presents a novel bottom-up holographic model incorporating string theory elements like tachyon condensation to better describe QCD phenomena.

Findings

Chiral symmetry breaking occurs at zero temperature.

Chiral symmetry is restored above the deconfinement transition.

The model's meson spectra and decay constants agree well with experimental data.

Abstract

A simple holographic model is presented and analyzed that describes chiral symmetry breaking and the physics of the meson sector in QCD. This is a bottom-up model that incorporates string theory ingredients like tachyon condensation which is expected to be the main manifestation of chiral symmetry breaking in the holographic context. As a model for glue the Kuperstein-Sonnenschein background is used. The structure of the flavor vacuum is analyzed in the quenched approximation. Chiral symmetry breaking is shown at zero temperature. Above the deconfinement transition chiral symmetry is restored. A complete holographic renormalization is performed and the chiral condensate is calculated for different quark masses both at zero and non-zero temperatures. The 0^{++},0^{-+},1^{++},1^{--} meson trajectories are analyzed and their masses and decay constants are computed. The asymptotic trajectories are linear. The model has one phenomenological parameter beyond those of QCD that affects the 1^{++},0^{-+} sectors. Fitting this parameter we obtain very good agreement with data. The model improves in several ways the popular hard-wall and soft wall bottom-up models.