Light-Front Holography and Novel Effects in QCD

TL;DR

This paper presents a semiclassical, relativistic model for strongly-coupled QCD using light-front holography, mapping AdS space to physical hadron wavefunctions, and discusses novel effects like confinement and hadronization.

Contribution

It introduces a single-variable light-front Schrödinger equation for QCD derived from AdS/QCD correspondence, providing new insights into hadron structure and confinement effects.

Findings

Derived a light-front Schrödinger equation for hadrons.

Confirmed the AdS/QCD correspondence through form factor mappings.

Discussed novel effects of confinement and a new hadronization method.

Abstract

The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. We identify the AdS coordinate $z$ with an invariant light-front coordinate $\zeta$ which separates the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single-variable light-front Schr\"odinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The mapping of electromagnetic and gravitational form factors in AdS space to their corresponding expressions in light-front theory confirms this correspondence. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates and the behavior of the QCD coupling in the infrared. The distinction between static structure functions such as the probability distributions computed from the square of the light-front wavefunctions versus dynamical structure functions which include the effects of rescattering is emphasized. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.