Baryons in Holographic QCD

TL;DR

This paper investigates baryons in holographic QCD by modeling them as topological solitons called Brane-induced Skyrmions, derived from a D4/D8/8 brane system, and compares the results with experimental data and standard Skyrmions.

Contribution

It derives a four-dimensional effective theory with pions and  ho-mesons from holographic QCD without small amplitude approximation, and numerically analyzes the properties of Brane-induced Skyrmions.

Findings

Obtained pion and  ho-meson profiles of the Skyrmion.

Estimated the total energy and size of the baryon model.

Compared the results with experimental baryon data and standard Skyrmions.

Abstract

We study the baryon in holographic QCD with $D4/D8/\bar{D8}$ multi-$D$ brane system. In holographic QCD, the baryon appears as a topologically non-trivial chiral soliton in a four-dimensional effective theory of mesons. We call this topological soliton as Brane-induced Skyrmion. Some review of $D4/D8/\bar{D8}$ holographic QCD is presented from the viewpoints of recent hadron physics and phenomenologies. Four-dimensional effective theory with pions and $\rho$ mesons is uniquely derived from the non-abelian Dirac-Born-Infeld (DBI) action of $D8$ brane with $D4$ supergravity background, without small amplitude expansion of meson fields to discuss chiral solitons. For the hedgehog configuration of pion and $\rho$-meson fields, we derive the energy functional and the Euler-Lagrange equation of Brane-induced Skyrmion from the meson effective action induced by holographic QCD. Performing the numerical calculation, we obtain the pion profile $F(r)$ and the $\rho$-meson profile $G(r)$ of the Brane-induced Skyrmion, and estimate its total energy, energy density distribution, and root-mean-square radius. These results are compared with the experimental quantities of baryons and also with the profiles of standard Skyrmion without $\rho$ mesons. We analyze interaction terms of pions and $\rho$ mesons in Brane-induced Skyrmion, and consider the role of $\rho$-meson component appearing in baryons.