Feynman’s Principle in Quantum Mechanics

Abstract

Richard P. Feynman was probably the greatest theoretical physicist of the second half of the 20th century. In his thesis work in 1942 at Princeton, Feynman attempted to solve the problem of the self mass of the electron, which is infinite in second-order perturbation theory in quantum electrodynamics.¹ Feynman discovered a “least action principle” that enabled him to solve the problem by using both retarded and advanced potentials. In order to do this, he introduced the mathematical concept of path integrals, which has been an extensive field of interest since then. The first triumph of this method came when it led to the correct calculation of the Lamb shift in the hydrogen atom without introducing any arbitrary cutoff parameters. The infinities were dealt with in a systematic and well-defined manner in terms of basic physical parameters. Since then, the renormalization group has acquired a depth that places it at the forefront of present theoretical physics.

You can never solve a problem on the level on which is was created. Albert Einstein