Speaker
Description
Light-front holography refers to an exact correspondance between semiclassical (with zero quark masses and no quantum loops) light-front QCD and a gravitational theory in 5-dimensional anti-de Sitter spacetime. Conformal symmetry is broken in a novel way, namely by the so-called dAFF (de Alfaro, Furbini and Furlan) mechanism which allows the emergence of a fundamental AdS/QCD mass scale $\kappa$ in the Hamiltonian while retaining the conformal invariance of the action. The AdS/QCD scale $\kappa$ sets the confinement scale as well as the mass scale for hadron spectroscopy in physical spacetime. Remarkably, the pion remains massless in the presence of a non-zero $\kappa$ just as expected in QCD for massless quarks. Superconformal algebra allows a unified description of mesons, baryons and tetraquarks spectroscopy. The AdS/QCD scale $\kappa$ is perhaps more fundamental than the familiar $\Lambda_{QCD}$ scale which emerges due to dimensional transmutation in perturbative QCD. In fact, by matching of the $\kappa$-dependent running strong coupling in the infrared to the $\Lambda_{QCD}$-dependent running strong coupling in perturbative QCD, the latter scale can be predicted from the former. Light-front holography serves as an excellent first approximation to hadron physics. Going beyond the semiclassical approximation, quark masses and their spins can be taken into account a posteriori, leading to successful unified description of observables involving light pseudoscalar and vector mesons using a single universal value of the AdS/QCD scale $\kappa$. Light-front holographic wavefunctions also serve as basis functions for Basis Light-Front Quantization which is a promising method for investigating non-perturbative QCD.
