Nonperturbative QCD Coupling and its $\beta$ function from Light-Front Holography

TL;DR

This paper derives a nonperturbative QCD coupling using light-front holography, showing it aligns with experimental data and models, and captures the transition from perturbative to nonperturbative regimes, supporting gauge/gravity duality in QCD.

Contribution

It introduces a nonperturbative effective coupling from light-front holography that matches data and models, extending predictions into the nonperturbative domain.

Findings

Effective coupling agrees with hadron physics data

Displays a transition at ~1 GeV between regimes

Captures key features of the QCD beta function

Abstract

The light-front holographic mapping of classical gravity in AdS space, modified by a positive-sign dilaton background, leads to a nonperturbative effective coupling $\alpha_s^{AdS}(Q^2)$. It agrees with hadron physics data extracted from different observables, such as the effective charge defined by the Bjorken sum rule, as well as with the predictions of models with built-in confinement and lattice simulations. It also displays a transition from perturbative to nonperturbative conformal regimes at a momentum scale $ \sim 1$ GeV. The resulting $\beta$ function appears to capture the essential characteristics of the full $\beta$ function of QCD, thus giving further support to the application of the gauge/gravity duality to the confining dynamics of strongly coupled QCD. Commensurate scale relations relate observables to each other without scheme or scale ambiguity. In this paper we extrapolate these relations to the nonperturbative domain, thus extending the range of predictions based on $\alpha_s^{AdS}(Q^2)$.