Infrateilchen in der Quantenfeldtheorie

Abstract

Abstract It is shown that in the presence of zero restmass particles the spectral assumptions of Quantum field theory have to be modified. Particles coupled to zero rest mass particles may not be eigenstates of the mass operator. In such a case the usual asymptotic condition is not valid and the Hilbertspace has an entirely different structure from the Hilbertspace of “normal” quantum field theory. Quantumelectrodynamics provides an example for this situation. The electron is an “infraparticle”, i. e. an “almost” discrete eigenstate of the mass operator.