Baryon charge from embedding topology and a continuous meson spectrum in a new holographic gauge theory

TL;DR

This paper introduces a new holographic gauge theory using probe D4-branes, revealing a continuous meson spectrum and providing a novel way to study baryons and nuclei through topological embeddings.

Contribution

It presents a holographic model with baryons as topologically nontrivial probe brane embeddings and uncovers a continuous meson spectrum, contrasting with typical discrete spectra in similar models.

Findings

Baryons correspond to smooth probe D4-brane embeddings with nontrivial topology.

The meson spectrum in this model is continuous, not discrete.

Small fluctuations are governed by a five-dimensional Maxwell action.

Abstract

We study a new holographic gauge theory based on probe D4-branes in the background dual to D4-branes on a circle with antiperiodic boundary conditions for fermions. Field theory configurations with baryons correspond to smooth embeddings of the probe D4-branes with nontrivial winding around an S^4 in the geometry. As a consequence, physics of baryons and nuclei can be studied reliably in this model using the abelian Born-Infeld action. However, surprisingly, we find that the meson spectrum is not discrete. This is related to a curious result that the action governing small fluctuations of the gauge field on the probe brane is the five-dimensional Maxwell action in Minkowski space despite the non-trivial embedding of the probe brane in the curved background geometry.