Towards a theory of bottom-up holographic models for linear Regge trajectories of light mesons

TL;DR

This paper develops a unified bottom-up holographic framework for modeling linear Regge trajectories of light mesons, integrating various existing models and exploring their interrelations.

Contribution

It introduces a general quadratic 5D holographic action that encompasses and unifies multiple Soft Wall models and new variants, linking them to key QCD phenomena.

Findings

Unified holographic models reproduce linear Regge spectra.

Different background modifications relate to confinement and chiral symmetry breaking.

Application to pion form factor aligns with experimental data.

Abstract

We advance in constructing a bottom-up holographic theory of linear meson Regge trajectories that generalizes and unites into one logical framework various bottom-up holographic approaches proposed in the past and scattered in the literature. The starting point of the theory is a quadratic in fields holographic five-dimensional action in which the Poincar\'{e} invariance along the holographic coordinate is violated in the most general way compatible with the linear Regge behavior of the discrete spectrum in four dimensions. It is further demonstrated how different Soft Wall (SW) like holographic models existing in the literature plus some new ones emerge from our general setup. Various interrelations between the emerging models are studied. These models include the known SW models with different sign in the exponential background, the SW models with certain generalized backgrounds, with modified metrics, and No Wall models with 5D mass depending on the holographic coordinate in a simple polynomial way. We argue that this dependence allows to describe the effects caused by the main non-local phenomena of strongly coupled 4D gauge theory, the confinement and chiral symmetry breaking, in terms of a local 5D dual field theory in the AdS space. We provide a detailed comparison of our approach with the Light Front holographic QCD, with the spectroscopic predictions of the dual Veneziano like amplitudes, and with the experimental Regge phenomenology. We apply our general approach to a holographic study of confinement, chiral symmetry breaking, and the pion form factor.