Chiral symmetry breaking as open string tachyon condensation

TL;DR

This paper presents a holographic model of chiral symmetry breaking via open string tachyon condensation, reproducing key QCD phenomena such as Goldstone bosons, the Gell-Mann-Oakes-Renner relation, and linear confinement of meson masses.

Contribution

It introduces a novel holographic framework where tachyon condensation drives chiral symmetry breaking and reproduces essential QCD features.

Findings

Reproduces N_f^2 Goldstone bosons for zero quark mass

Derives the Gell-Mann-Oakes-Renner relation for small quark mass

Shows linear Regge trajectories for highly excited mesons

Abstract

We consider a general framework to study holographically the dynamics of fundamental quarks in a confining gauge theory. Flavors are introduced by placing a set of (coincident) branes and antibranes on a background dual to a confining color theory. The spectrum contains an open string tachyon and its condensation describes the U(N_f)_L x U(N_f)_R -> U(N_f)_V symmetry breaking. By studying worldvolume gauge transformations of the flavor brane action, we obtain the QCD global anomalies and an IR condition that allows to fix the quark condensate in terms of the quark mass. We find the expected N_f^2 Goldstone bosons (for m_q=0), the Gell-Mann-Oakes-Renner relation (for m_q small) and the \eta' mass. Remarkably, the linear confinement behavior for the masses of highly excited spin-1 mesons, m_n^2 ~ n is naturally reproduced.