NJL and QCD from String Theory

TL;DR

This paper explores a D-brane configuration in string theory that models both NJL and QCD, showing how the system interpolates between these theories and exhibits chiral symmetry breaking at various couplings.

Contribution

It introduces a D-brane setup that smoothly transitions between NJL and QCD, providing a unified string-theoretic framework for studying chiral symmetry breaking.

Findings

The low-energy theory is a non-local NJL model at certain parameters.

The model is exactly solvable at large N_c and shows chiral symmetry breaking.

The system interpolates between NJL and QCD depending on parameters.

Abstract

We study a configuration of D-branes in string theory that is described at low energies by a four-dimensional field theory with a dynamically broken chiral symmetry. In a certain region of the parameter space of the brane configuration the low-energy theory is a non-local generalization of the Nambu-Jona-Lasinio (NJL) model. This vector model is exactly solvable at large N_c and dynamically breaks chiral symmetry at arbitrarily weak 't Hooft coupling. At strong coupling the dynamics is determined by the low-energy theory on D-branes living in the near-horizon geometry of other branes. In a different region of parameter space the brane construction gives rise to large N_c QCD. Thus the D-brane system interpolates between NJL and QCD.