  The AdS/CFT correspondence between string theory in AdS space and conformal
field theories in physical space-time leads to an analytic, semi-classical
model for strongly-coupled QCD which has scale invariance and dimensional
counting at short distances and color confinement at large distances. The
AdS/CFT correspondence also provides insights into the inherently
non-perturbative aspects of QCD such as the orbital and radial spectra of
hadrons and the form of hadronic wavefunctions. In particular, we show that
there is an exact correspondence between the fifth-dimensional coordinate of
anti-de Sitter (AdS) space $z$ and a specific light-front impact variable
$\zeta$ which measures the separation of the quark and gluonic constituents
within the hadron in ordinary space-time. This connection allows one to compute
the analytic form of the frame-independent light-front wavefunctions of mesons
and baryons, the fundamental entities which encode hadron properties and which
allow the computation of decay constants, form factors and other exclusive
scattering amplitudes. Relativistic light-front equations in ordinary
space-time are found which reproduce the results obtained using the
fifth-dimensional theory. As specific examples we compute the pion coupling
constant $f_\pi$, the pion charge radius $< r_\pi^2 >$ and examine the
propagation of the electromagnetic current in AdS space, which determines the
space and time-like behavior of the pion form factor and the pole of the $\rho$
meson.

High Energy Physics - Phenomenology;High Energy Physics - Theory