Relativistic approaches to investigation of few-nucleon systems

Theoretical approaches used in investigation of relativistic effects in high energy lepton and hadron collisions with few-nucleon systems are analyzed. The Bethe-Salpeter formalism for describing interacting systems of two spinor particles both in the continuum and bound state is described in detail. Special attention is paid to partial expansions, taking into account the analytic properties of Bethe-Salpeter amplitudes and unitary transformations correlating different representations of partial amplitudes. Mathematical methods of numerical solution of equations are considered. Results of calculation of relativistic corrections and effects of interaction in the final state in particular reactions with participation of the deuteron, namely, in elastic pD backward scattering and in reactions of deuteron break-up with production of correlated pairs, are presented.