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Relativistic Formulation of Reaction Theory

A relativistic formulation of reaction theory for nuclei with a dynamics given by a unitary representations of the Poincaré group is developed. Relativistic dynamics is introduced by starting from a relativistic theory of free particles to which rotationally invariant interactions are added to the invariant mass operator. Poincaré invariance is realized by requiring that simultaneous eigenstates of the mass and spin transform as irreducible representations of the Poincaré group. A relativistic formulation of scattering theory is presented and approximations emphasizing dominant degrees of freedom that preserve unitarity, exact Poincaré invariance and exchange symmetry are discussed. A Poincaré invariant formulation of a (d,p) reaction as a three-body problem is given as an explicit example.