QCD domain walls, Chern-Simons theories and holography

TL;DR

This paper uses holographic QCD to analyze domain walls in massive QCD at θ=π, confirming theoretical expectations and exploring claims about 3D physics and quantum phases in Chern-Simons theories.

Contribution

It demonstrates that the Witten-Sakai-Sugimoto model reproduces QCD domain wall phenomena and supports claims about 3D physics and quantum phases in Chern-Simons theories.

Findings

Model reproduces QCD domain wall behavior.

Supports the claim that domain-wall theory is fully 3D.

Provides evidence for quantum phases in Chern-Simons theories.

Abstract

Massive QCD at $\theta=\pi$ breaks CP spontaneously and admits domain walls whose dynamics and phases depend on the number of flavors and their masses. We discuss these issues within the Witten-Sakai-Sugimoto model of holographic QCD. Besides showing that this model reproduces all QCD expectations, we address two interesting claims in the literature. The first is about the possibility that the QCD domain-wall theory is fully captured by three-dimensional physics, only. The second regards the existence of quantum phases in certain Chern-Simons theories coupled to fundamental matter. Both claims are supported by the string theory construction.