  A remarkable holographic feature of dynamics in AdS space in five dimensions
is that it is dual to Hamiltonian theory in physical space-time, quantized at
fixed light-front time {\tau} = t+z/c. This light-front holographic principle
provides a precise relation between the bound-state amplitudes in AdS space and
the boost-invariant light-front wavefunctions describing the internal structure
of hadrons in physical space-time. The fifth dimension coordinate z is dual to
the light front variable {\zeta} describing the invariant separation of the
quark constituents. The resulting valence Fock-state wavefunction
eigensolutions of the light-front QCD Hamiltonian satisfy a single-variable
relativistic equation of motion, analogous to the nonrelativistic radial
Schr\"odinger equation. The soft-wall dilaton profile exp ({\kappa}^2
{\zeta}^2) provides a model for the light-front potential which is
color-confining and reproduces well the linear Regge behavior of the
light-quark hadron spectrum in both L, the orbital angular momentum, and n, the
radial node number. The pion mass vanishes in the chiral limit and other
features of chiral symmetry are satisfied. The resulting running QCD coupling
displays an infrared fixed point. The elastic and transition form factors of
the pion and the nucleons are also found to be well described in this
framework. The light-front AdS/QCD holographic approach thus gives a
frame-independent analytic first approximation of the color-confining dynamics,
spectroscopy, and excitation spectra of relativistic light-quark bound states
in QCD.
