The Mechanics of Lagrange

Abstract

The most general starting point for the discussion of any mechanical system is the variational principle. It was first proposed as a particularly concise formulation of Newton’s laws of motion, and it turns out to be extremely useful for some simple manipulations such as the transition between different coordinate systems. (Feynman, 1948, 1965), with the inspiration of Dirac (1933, 1935), then found a complete analog for it in quantum mechanics. Indeed, the path integral provides the most direct link between the classical and the quantum regime (cf. Section 13.4).