The significance of the correspondence between the classical limit of quantum theories and the laws of classical physics is explained.It is proved that this correspondence yields constraints on acceptable quantum theories.The variational principle is taken as the basis of the analysis.The discussion shows that the first order Dirac equation abides by these constraints, whereas second order quantum equations fail to do that.
The significance of the correspondence between the classical limit of quantum theories and the laws of classical physics is explained.It is proved that this correspondence yields constraints on acceptable quantum theories.The variational principle is taken as the basis of the analysis.The discussion shows that the first order Dirac equation abides by these constraints, whereas second order quantum equations fail to do that.
The paper examines the Dirac-Pauli differences concerning the order of the primary differential equation of an elementary massive quantum particle.The analysis relies on several self-evident constraints that an acceptable quantum theory must satisfy, like conservation laws, compatibility with Maxwellian electrodynamics and the correspondence principle.The dimension of the quantum function that is used in the Lagrangian density of a given quantum theory together with the corresponding differential equations play an important role in the reasoning procedure.The paper proves that Dirac was right and that second-order quantum theories like the Klein-Gordon equation and the electroweak theory of the W ± bosons do not satisfy fundamental constraints.This outcome is inconsistent with the Standard Model of Particle Physics.
The foundations of the mathematical structure of quantum theories of a massive particle are the basis of this analysis.It proves the coherence of the particle-wave duality of quantum theories and the principle of complementarity as well.Furthermore, the noncommutativity of Hermitian operators proves that quantum theories are inherently indeterministic.This feature does not deny the fact that the classical limit of quantum theories agrees with classical physics.It is also shown that the foundations of the mathematical structure of quantum theories impose constraints on any specific quantum theory.It is proved that the first-order Dirac theory is consistent with all constraints.In contrast, second-order theories, such as the Klein-Gordon, the electroweak theory of the W ± and the Z particles, and the Higgs boson theory fail to do that.An analogous analysis proves that also the Majorana neutrino theory is inconsistent with fundamental requirements.Similarly, inconsistencies of Proca's idea about a massive photon are shown.
The paper shows that the variational principle serves as an element of the mathematical structure of a quantum theory. The experimentally confirmed properties of the corpuscular-wave duality of a quantum particle are elements of the analysis. A Lagrangian density that yields the equations of motion of a given quantum theory of a massive particle is analyzed. It is proved that if this Lagrangian density is a Lorentz scalar whose dimension is then the associated action consistently defines the required phase of the quantum particle. The dimension of this Lagrangian density proves that also the quantum function has dimension. This result provides new criteria for the acceptability of quantum theories. An examination of the first order Dirac equation demonstrates that it satisfies the new criteria whereas the second order Klein-Gordon equation fails to do that.
The fact that the Schr\"odinger and the Dirac equations for the wave function of an electron are differential equations of the first order with respect to time, while in classical theories differential equations of the second order are common, has necessitated a slightly different setup of the canonical theory in both fields. Under influence of the classical methods, second-order equations are also often used in the quantum theory of particles of integer spin, thus causing a difference between the treatment of Fermi-Dirac and of Einstein-Bose particles.It is shown here that conformity between classical and quantum-mechanical methods can be achieved easily by use of first-order equations throughout, thus avoiding a superfluous distinction between integral and half-odd-integral spin fields. The classical theory of a point charge in an electromagnetic field of force is set up here from this point of view.
We propose six principles as the fundamental principles of quantum mechanics: principle of space and time, Galilean principle of relativity, Hamilton's principle, wave principle, probability principle, and principle of indestructibility and increatiblity of particles. We deductively develop the formalism of quantum mechanics on the basis of them: we determine the form of the Lagrangian that satisfies requirements of these principles, and obtain the Schroedinger equation from the Lagrangian. We also derive the canonical commutation relations. Then we adopt the following four guide lines. First, we do not premise the relations between dynamical variables in classical mechanics. Second, we define energy, momentum, and angular momentum as the constants of motion that are derived from homogeneity and isotropy in space and time on the basis of principle of space and time. Since energy and momentum are quantitatively defined in classical mechanics, we define them in quantum mechanics so that the corresponding conservation laws are satisfied in a coupling system of a quantum particle and a classical particle. Third, we define Planck's constant and the mass of a particle as proportionality constants between energy and frequency due to one of Einstein-de Broglie formulas and between momentum and velocity, respectively. We shall obtain the canonical commutation relations and the Schroedinger equation for a particle in an external field in the definitive form. We shall also prove that relations between dynamical variables in quantum mechanics have the same forms for those in classical mechanics.
This paper re-examines the key aspects of Dirac's derivation of his relativistic equation for the electron in order advance our understanding of the nature of quantum field theory. Dirac's derivation, the paper argues, follows the key principles behind Heisenberg's discovery of quantum mechanics, which, the paper also argues, transformed the nature of both theoretical and experimental physics vis-a-vis classical physics and relativity. However, the limit theory (a crucial consideration for both Dirac and Heisenberg) in the case of Dirac's theory was quantum mechanics, specifically, Schrodinger's equation, while in the case of quantum mechanics, in Heisenberg's version, the limit theory was classical mechanics. Dirac had to find a new equation, Dirac's equation, along with a new type of quantum variables, while Heisenberg, to find new theory, was able to use the equations of classical physics, applied to different, quantum-mechanical variables. In this respect, Dirac's task was more similar to that of Schrodinger in his work on his version of quantum mechanics. Dirac's equation reflects a more complex character of quantum electrodynamics or quantum field theory in general and of the corresponding (high-energy) experimental quantum physics vis-a-vis that of quantum mechanics and the (low-energy) experimental quantum physics. The final section examines this greater complexity and its implications for fundamental physics.