The light-front quantization of gauge theories such as QCD in light-cone
gauge provides a frame-independent wavefunction representation of relativistic
bound states, simple forms for current matrix elements, explicit unitarity, and
a trivial vacuum. The freedom to choose the light-like quantization four-vector
provides an explicitly covariant formulation of light-front quantization and
can be used to determine the analytic structure of light-front wave functions
and to define a kinematical definition of angular momentum. The AdS/CFT
correspondence of large NCβ supergravity theory in higher-dimensional anti-de
Sitter space with supersymmetric QCD in 4-dimensional space-time has
interesting implications for hadron phenomenology in the conformal limit,
including an all-orders demonstration of counting rules for exclusive
processes. String/gauge duality also predicts the QCD power-law behavior of
light-front Fock-state hadronic wavefunctions with arbitrary orbital angular
momentum at high momentum transfer. The form of these near-conformal
wavefunctions can be used as an initial ansatz for a variational treatment of
the light-front QCD Hamiltonian. I also briefly review recent analyses which
shows that some leading-twist phenomena such as the diffractive component of
deep inelastic scattering, single-spin asymmetries, nuclear shadowing and
antishadowing cannot be computed from the LFWFs of hadrons in isolation.Comment: Presented at LightCone 2004, Amsterdam, The Netherlands, 16-20 August
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