Cosmic Topological Defects from Holography

TL;DR

This paper explores cosmic topological defects such as strings and domain walls in gauge theories using holographic models, revealing phase transitions and topological phases relevant to the early universe.

Contribution

It provides a holographic description of cosmic defects, including a phase transition and a topological phase of matter, in a specific gauge theory model.

Findings

Identification of a first-order phase transition between string and domain wall solutions.

Description of vortons as excitations in a topological phase with Chern-Simons theory.

Effective mesonic description of string loops and vortons.

Abstract

This work investigates cosmic topological defects in gauge theories, focusing on models with an $SU(N)$ gauge group coupled with a single flavor, explored through a holographic framework. At low energies, the effective theory is described by an axion-like particle resulting from the spontaneous breaking of the axial $U(1)_A$ flavor symmetry. As the Universe cools below a critical temperature, the chiral symmetry is broken, and non-trivial vacuum configurations form, resulting in the creation of cosmic strings and domain walls. We provide a UV description of these defects in a particular holographic theory, the Witten-Sakai-Sugimoto model, as probe D6-branes. We show the presence of a first-order phase transition separating string loop from domain wall solutions. String loops charged under the baryon symmetry and with angular momentum - vortons - can be understood as excitations of a topological phase of matter given by a Chern-Simons theory living on the D6-brane world volume. Finally, we provide an effective description of string loops and vortons in terms of degrees of freedom living on the flavor brane, i.e. mesonic modes.