QUANTUM CHROMODYNAMICS AND OTHER FIELD-THEORIES ON THE LIGHT-CONE

In recent years light-cone quantization of quantum field theory has em erged as a promising method for solving problems in the strong couplin g regime. The approach has a number of unique features that make it pa rticularly appealing, most notably, the ground state of the free theor y is also a ground state of the full theory. We discuss the light-cone quantization of gauge theories from two perspectives: as a calculatio nal tool for representing hadrons as QCD bound states of relativistic quarks and gluons, and also as a novel method for simulating quantum f ield theory on a computer. The light-cone Fock state expansion of wave functions provides a precise definition of the parton model and a gene ral calculus for hadronic matrix elements. We present several new appl ications of light-cone Fock methods, including calculations of exclusi ve weak decays of heavy hadrons, and intrinsic heavy-quark contributio ns to structure functions. A general non-perturbative method for numer ically solving quantum held theories, ''discretized light-cone quantiz ation'', is outlined and applied to several gauge theories. This metho d is invariant under the large class of light-cone Lorentz transformat ions, and it can be formulated such that ultraviolet regularization is independent of the momentum space discretization. Both the bound-stat e spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the struct ure of the light-cone vacuum, and outline the renormalization techniqu es required for solving gauge theories within the Hamiltonian formalis m on the light cone. (C) 1998 Elsevier Science B.V. All rights reserve d.