A Lorentz invariant theoretical model for a particle with spin

A general postulate for a free particle with spin is formulated, and from this postulate is obtained Lorentz mechanics for a particle with spin in an electromagnetic field. Interaction of the spin with the field is taken into account. From this treatment the Zeeman and Stark effects can be deduced, as well as Stern-Gerlach.Quantum mechanics for a particle with spin in an electromagnetic field can also be obtained, by replacing in the usual way momentum and spin in the energy equation by the corresponding operators. The application of this quantum theory to the hydrogen atom gives similar energy levels as the Theory of Dirac. Furthermore, the theory is applicable to proton and neutron. By this general postulate it is also possible to give a linear Lorentz invariant gravitation theory, which is in full agreement with known tests of the general theory of relativity