Theta angle in holographic QCD

TL;DR

This paper explores the effects of the theta angle in holographic QCD models, specifically V-QCD, analyzing phase diagrams and observables like topological susceptibility and meson masses across various parameters.

Contribution

It introduces a comprehensive holographic model that incorporates the theta angle and axial anomaly, providing new insights into QCD phase structure and observables.

Findings

V-QCD models include the theta angle and axial anomaly.

Results agree with chiral Lagrangians at small quark mass.

Phase diagrams are mapped over quark mass, N_f/N_c, and theta.

Abstract

V-QCD is a class of effective holographic models for QCD which fully includes the backreaction of quarks to gluon dynamics. The physics of the theta-angle and the axial anomaly can be consistently included in these models. We analyze their phase diagrams over ranges of values of the quark mass, N_f/N_c, and theta, computing observables such as the topological susceptibility and the meson masses. At small quark mass, where effective chiral Lagrangians are reliable, they agree with the predictions of V-QCD.