Purturbation

Full Title

from Born

What we shall do, is to bring the classical laws for the perturbation of a mechanical system, caused by internal couplings or external fields, into one and the same form, which would very strongly suggest the formal passage from classical mechanics to a 'quantum mechanics'. For this, the quantum rules as such will be retained essentially unchanged; as multiples of the action quantum h there will appear the action integrals of the unperturbed system, 4) which is assumed to be separable and non-degenerate. On the other hand, mechanics itself will undergo a change, in the sense of a transition from differential to difference equations, as already exhibited by Bohr's frequency conditions. In the simple case of non-degenerate systems, there seems then to be no room left for arbitrariness.

Context

“The breakdown of the continuum approximation" is the most accurate, widely accepted description for what is called here Discrete Physical Models.