  Within the general setting of algebraic quantum field theory, a new approach
to the analysis of the physical state space of a theory is presented; it covers
theories with long range forces, such as quantum electrodynamics. Making use of
the notion of charge class, which generalizes the concept of superselection
sector, infrared problems are avoided. In fact, on this basis one can determine
and classify in a systematic manner the proper charge content of a theory, the
statistics of the corresponding states and their spectral properties. A key
ingredient in this approach is the fact that in real experiments the arrow of
time gives rise to a Lorentz invariant infrared cutoff of a purely geometric
nature.
