Holographic two dimensional QCD and Chern-Simons term

TL;DR

This paper constructs a holographic model of two-dimensional massless QCD with large Nc, highlighting the role of a three-dimensional Chern-Simons term in meson spectra, anomaly effects, and photon mass generation.

Contribution

It introduces a D2/D8 brane holographic setup for 2D QCD, emphasizing the impact of the Chern-Simons term on anomalies and meson dynamics, which is a novel approach.

Findings

Chern-Simons term affects meson spectrum and holographic renormalization

Massless flavor bosons decouple from heavier mesons

External photon acquires mass via Schwinger mechanism

Abstract

We present a holographic realization of large Nc massless QCD in two dimensions using a D2/D8 brane construction. The flavor axial anomaly is dual to a three dimensional Chern-Simons term which turns out to be of leading order, and it affects the meson spectrum and holographic renormalization in crucial ways. The massless flavor bosons that exist in the spectrum are found to decouple from the heavier mesons, in agreement with the general lore of non-Abelian bosonization. We also show that an external dynamical photon acquires a mass through the three dimensional Chern-Simons term as expected from the Schwinger mechanism. Massless two dimensional QCD at large Nc exhibits anti-vector-meson dominance due to the axial anomaly.