The Physical State Space of Quantum Electrodynamics

Abstract

One consequence of the possible appearance of infrared clouds is that in quantum electrodynamics there are innumerably many sectors satisfying the Borchers selection criterion even for states with the same charge. It is then convenient to make a coarser distinction and combine all sectors which coincide in their information about the content of outgoing (or incoming) massive particles in their respective folia of states into one class. Since electrically charged particles are massive such a class fixes in particular the electric charge and for this reason it was called a charge class in [Buch 82b]. We shall keep this terminology here though these classes still give a much finer distinction than that provided by the charge quantum numbers.