Relativistic Energy-Momentum & Relativistic Quantum Mechanics

The relativistic energy-momentum relationship is far more subtle than it seems to be at a first sight. As concerns the relativistic quantum mechanics, its underlying equations were deduced from, or in relation with the relativistic energy-momentum relationship by means of the principle of correspondence. Without a clear physical role and meaning associated, the matrices of the Dirac equation seemed to confirm that the principle of the physical determination of equations would not be proper to the new quantum mechanics. Therefore, we have to search for genuine physical information in the terms of the underlying equations of the relativistic quantum mechanics. This information concerns a level of structure of matter “even below that on which nuclear transformations take place.”