  The QCD light-front Hamitonian equation derived from quantization at fixed LF
time provides a causal, frame-independent, method for computing hadron
spectroscopy and dynamical observables. de Alfaro, Fubini, and Furlan (dAFF)
have made an important observation that a mass scale can appear in the
equations of motion without affecting the conformal invariance of the action if
one adds a term to the Hamiltonian proportional to the dilatation operator or
the special conformal operator. If one applies the dAFF procedure to the QCD
light-front Hamiltonian, it leads to a color confining potential $\kappa^4
\zeta^2$ for mesons, where $\zeta^2$ is the LF radial variable conjugate to the
$q \bar q$ invariant mass squared. The same result, including spin terms, is
obtained using light-front holography if one modifies the AdS$_5$ action by the
dilaton $e^{\kappa^2 z^2}$ in the fifth dimension $z$. When one generalizes
this procedure using superconformal algebra, the resulting light-front
eigensolutions provide a unified Regge spectroscopy of meson, baryon, and
tetraquarks, including remarkable supersymmetric relations between the masses
of mesons and baryons and a universal Regge slope. The pion $q \bar q$
eigenstate has zero mass at $m_q=0.$ The superconformal relations also can be
extended to heavy-light quark mesons and baryons. AdS/QCD also predicts the
analytic form of the nonperturbative running coupling in agreement with the
effective charge measured from measurements of the Bjorken sum rule. The mass
scale underlying hadron masses can be connected to the mass parameter in the
QCD running coupling. The result is an effective coupling $\alpha_s(Q^2)$
defined at all momenta. One also obtains empirically viable predictions for
spacelike and timelike hadronic form factors, structure functions, distribution
amplitudes, and transverse momentum distributions.
