Skyrmions with holography and hidden local symmetry

TL;DR

This paper compares holographic QCD and hidden local symmetry models for baryons as Skyrmions, revealing how extra-dimensional curvature influences vector meson roles and stabilizes Skyrmions.

Contribution

It demonstrates the impact of extra-dimensional curvature on vector meson configurations and Skyrmion stability in holographic QCD versus HLS models.

Findings

Rho-meson acts as a stabilizer in HLS with singular configuration.

In holographic QCD, rho-meson has a regular configuration, providing weak attraction.

Skyrmion stability is achieved in holographic QCD due to extra-dimensional effects.

Abstract

We study baryons as Skyrmions in holographic QCD with D4/D8/D8-bar multi-D brane system in type IIA superstring theory, and also in the non-linear sigma model with hidden local symmetry (HLS). Comparing these two models, we find that the extra-dimension and its nontrivial curvature can largely change the role of (axial) vector mesons for baryons in four-dimensional space-time. In the HLS approach, the rho-meson field as a massive Yang-Mills field has a singular configuration in Skyrmion, which gives a strong repulsion for the baryon as a stabilizer. When a_1 meson is added in this approach, the stability of Skyrmion is lost by the cancellation of rho and a_1 contributions. On the contrary, in holographic QCD, the rho-meson field does not appear as a massive Yang-Mills field due to the extra-dimension and its nontrivial curvature. We show that the rho-meson field has a regular configuration in Skyrmion, which gives a weak attraction for the baryon in holographic QCD. We argue that Skyrmion with pi, rho and a_1 mesons become stable due to the curved extra-dimension and also the presence of the Skyrme term in holographic QCD. From this result, we also discuss the features of our truncated-resonance analysis on baryon properties with pi and rho mesons below the cutoff scale M_KK about 1GeV in holographic QCD, which is compared with other 5D instanton analysis.