AdS/QCD: The Relevance of the Geometry

TL;DR

This paper examines how the geometry of five-dimensional models influences hadron physics, finding that the metric's impact is limited but a decreasing warp factor like AdS space is preferred, and simplified models can replicate key features.

Contribution

It demonstrates that the metric's shape has limited effect on results, highlights the preference for AdS-like geometry, and shows simple three-site models can reproduce holographic QCD features.

Findings

Flat space models agree reasonably with data.

Preference for decreasing warp factor, e.g., AdS space.

Simple 3-site models capture essential holographic QCD features.

Abstract

We investigate the relevance of the metric and of the geometry in five-dimensional models of hadrons. Generically, the metric does not affect strongly the results and even flat space agrees reasonably well with the data. Nevertheless, we observe a preference for a decreasing warp factor, for example AdS space. The Sakai-Sugimoto model reduces to one of these models and the level of agreement is similar to the one of flat space. We also consider the discrete version of the five-dimensional models, obtained by dimensional deconstruction. We find that essentially all the relevant features of "holographic" models of QCD can be reproduced with a simple 3-site model describing only the states below the cut-off of the theory.