EQUIVALENCE PRINCIPLE AND DISCRETE SYMMETRIES OF DIRAC AND MAJORANA FERMIONS IN GRAVITATIONAL-FIELD

The discrete symmetries of the Dirac and Majorana fermions in an exter nal gravitational field are studied in the weak-field approximation. A llowing the presence of other particle interactions (strong, electroma gnetic, weak and unknown interactions) the most general expression for the gravitational form factors of the fermion is obtained. It is show n that the Dirac fermion can be used to test the generalized strong-eq uivalence principle (including quantum spin) whether the interaction c onserved CP or not. For the Majorana fermion, one requires the interac tion is CP violating but CPT invariant in order to test the principle.