%0 Journal Article
%T Hamiltonian, Lagrangian and Physical Laws
%A E. Comay
%J Open Access Library Journal
%V 6
%N 7
%P 1-11
%@ 2333-9721
%D 2019
%I Open Access Library
%R 10.4236/oalib.1105536
%X <div style="text-align:justify;">
	<span style="line-height:1.5;">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.</span> 
</div>
%K The Correspondence Principle
%K Constraints on Quantum Theories
%K the Variational Principle
%K First Order Quantum Equations
%K Second Order Quantum Equations
%U http://www.oalib.com/paper/5393428