Oskar Klein The Dirac Theory of the Electron in General Relativity Theory

Abstract

The Swedish physicist Oskar Klein 1894–1977 was an important contributor to the developments of modern quantum physics. The foundations were laid in Copenhagen under the inspired guidance of Niels Bohr. Klein became here a trusted collaborator with the leading physicists in the field and played a central role in combining these new ideas with Einstein's theory of relativity. His most important contribution came from his realization that electromagnetism could be understood as an extension of Einstein's general theory of relativity to a curved spacetime with one extra dimension. The same idea had been suggested by the German mathematician Kaluza a few years earlier. But it was Klein who made it more acceptable by using quantum mechanics and showing that the extra dimension could be made microscopically small and therefore unobservable in present-day experiments. In connection with this work he also obtained the relativistic theory for bosons as described by what today is called the Klein-Gordon wave equation. After a short biographical summary of the scientific life of Oskar Klein, a more pedagogic presentation of these ideas is given with special emphasis on the fivedimensional framework he used. His contribution to DKNVS was an attempt to also describe fermions in such curved spacetimes.