Chiral currents and static properties of nucleons in holographic QCD

TL;DR

This paper investigates nucleon static properties using holographic QCD, constructing a chiral current from a five-dimensional model, and finds results closer to experiments than traditional Skyrme models.

Contribution

It introduces a method to derive a chiral current in holographic QCD and applies it to compute nucleon properties, improving agreement with experimental data.

Findings

Charge radii and magnetic moments are closer to experimental values.

The chiral current construction reveals gauge invariance issues.

Most nucleon properties computed are more accurate than in Skyrme models.

Abstract

We analyze static properties of nucleons in the two flavor holographic QCD model of Sakai and Sugimoto described effectively by a five-dimensional U(2) Yang-Mills theory with the Chern-Simons term on a curved background. The baryons are represented in this model as a soliton, which at a time slice is approximately the BPST instanton with a fixed size. First, we construct a chiral current in four dimensions from the Noether current of local gauge transformations which are non-vanishing on the boundaries of the extra dimension. We examine this chiral current for nucleons with quantized collective coordinates to compute their charge distribution, charge radii, magnetic moments and axial vector coupling. Most of the results are better close to the experimental values than in the Skyrme model. We discuss the problems of our chiral current; non-uniqueness of the local gauge transformation for defining the current, and its gauge-noninvariance.