Euclidean Correlation Functions in a Holographic Model of QCD

TL;DR

This paper computes Euclidean correlation functions in a simple holographic QCD model, successfully capturing key features like anomaly effects and low energy theorems, and compares results with instanton-based models.

Contribution

It demonstrates that a basic holographic model on AdS_5 can qualitatively reproduce QCD correlation functions, including anomaly and positivity properties.

Findings

Qualitative agreement with QCD correlation functions

Correct implementation of anomaly-related positivity and theorems

Comparison with instanton model results

Abstract

We compute euclidean coordinate space correlation functions in a holographic model of QCD. We concentrate, in particular, on channels that are related to the U(1)_A problem, the flavor-singlet axialvector, pseudoscalar meson, and pseudoscalar glueball (topological charge) correlator. We find that even a very simple holographic model defined on a slice of AdS_5 provides a qualitatively correct description of QCD correlation functions. We study the role of anomaly terms, and show that both euclidean positivity and low energy theorems based on the axial anomaly relation are correctly implemented. We compare the results with expectations from an instanton model of the QCD vacuum.