We discuss the weak amplitudes which determine the parity violating nuclear force. By use of the quark model and the SU(6), symmetry, we unite the treatment of pion and vector meson vertices, and describe the interrelation of past techniques which have been applied to this problem. This allows us to catalog the uncertainties in the amplitudes, and to provide reasonable bounds on their values. The connection of OUT results with experiment is also discussed.

The wave function of a composite system is defined in relativity on a space-time surface. In the explicitly covariant light-front dynamics, reviewed in the present article, the wave functions are defined on the plane ω·x = 0, where ω is an arbitrary four-vector with ω 2 = 0. The standard non-covariant approach is recovered as a particular case for ω = (1, 0, 0, −1). Using the light-front plane is of crucial importance, while the explicit covariance gives strong advantages emphasized through all the review.The properties of the relativistic few-body wave functions are discussed in detail and are illustrated by examples in a solvable model. The three-dimensional graph technique for the calculation of amplitudes in the covariant light-front perturbation theory is presented.The structure of the electromagnetic amplitudes is studied. We investigate the ambiguities which arise in any approximate light-front calculations, and which lead to a non-physical dependence of the electromagnetic amplitude on the orientation of the lightfront plane. The elastic and transition form factors free from these ambiguities are found for spin 0, 1/2 and 1 systems.The formalism is applied to the calculation of the relativistic wave functions of twonucleon systems (deuteron, scattering state), with particular attention to the role of their new components in the deuteron elastic and electrodisintegration form factors and to their connection with meson exchange currents. Straigthforward applications to the pion and nucleon form factors and the ρ − π transition are also made. ,0 = − 2η(F 1 − ηF 2 + G 1 /2) + η/2B 6 ,(6.63)The matrix elementsJ 11 ,J 1−1 have the same form as J 11 , J 1−1 , whereasJ 10 ,J 00 differ from J 10 , J 00 by the items containing the nonphysical form factors B 5 , B 6 , B 7 . Other nonphysical form factors B 1−4 and B 8 do not contribute to these matrix elements.The matrix elementsJ λ ′ λ do not satisfy the condition (6.61). SubstitutingJ λ ′ λ in eq.(6.61) instead of J λ ′ λ , we get: ∆ ≡ (1 + 2η)J 11 +J 1−1 − 2 2ηJ 10 −J 00 = −(B 5 + B 7 ) .(6.64)

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π and η decay modes of light baryon resonances are investigated within a chiral quark model whose hyperfine interaction is based on Goldstone-boson exchange. For the decay mechanism a modified version of the 3 P0 model is employed. Our primary aim is to provide a further test of the recently proposed Goldstone-boson-exchange constituent quark model. We compare the predictions for π and η decay widths with experiment and also with results from a traditional one-gluon-exchange constituent quark model. The differences between nonrelativistic and semirelativistic versions of the constituent quark models are outlined. We also discuss the sensitivity of the results on the parametrization of the meson wave function entering the 3 P0 model.