An AdS/QCD model from Sen's tachyon action

TL;DR

The paper develops a phenomenological AdS/QCD model that embeds Sen's brane-antibrane tachyon action to generate chiral symmetry breaking in a confining AdS background. The bulk contains two gauge fields and a complex tachyon whose IR divergence encodes the quark condensate, leading to meson towers obtained from linearized bulk fluctuations. The resulting low-spin spectra agree with PDG values at the 10–15% level, while exhibiting Regge-like trajectories and a deconfinement temperature near 208 MeV; the approach improves on prior hard- and soft-wall models by dynamically generating the condensate and capturing quark-mass dependence. This compact framework offers a controlled, string-inspired route to approximate QCD spectra and motivates extensions to non-Abelian, multi-flavor sectors.

Abstract

We construct a new, simple phenomenological model along the lines of AdS/QCD. The essential new ingredient is the brane-antibrane effective action including the open string tachyon proposed by Sen. Chiral symmetry breaking happens because of tachyon dynamics. We fit a large number of low-spin meson masses at the 10%-15% level. The only free parameters involved in the fits correspond to the overall QCD-scale and the quark masses. Several aspects of previous models are qualitatively improved.