Chiral Dynamics of Baryons from String Theory

TL;DR

This paper models baryons using string theory within the AdS/CFT framework, deriving effective actions and calculating key properties like axial coupling and magnetic moments, with results scaled by the number of colors.

Contribution

It introduces a novel effective field theory for baryons in a string theory context, connecting instanton descriptions to observable baryonic properties.

Findings

Estimated axial coupling $g_A$ consistent with experimental values

Calculated magnetic dipole moments proportional to $N_c$

Reproduced chiral effective action through dimensional reduction

Abstract

We study baryons in an AdS/CFT model of QCD by Sakai and Sugimoto, realized as small instantons with fundamental string hairs. We introduce an effective field theory of the baryons in the five-dimensional setting, and show that the instanton interpretation implies a particular magnetic coupling. Dimensional reduction to four dimensions reproduces the usual chiral effective action, and in particular we estimate the axial coupling $g_A$ between baryons and pions and the magnetic dipole moments, both of which are proportional to $N_c$. We extrapolate to finite $N_c$ and discuss subleading corrections.