# New Light on Infrared Problems: Sectors, Statistics, Symmetries and Spectrum

April 09, 2013

A new approach to the analysis of the physical state space of a theory is
presented within the general setting of local quantum physics. It also covers
theories with long range forces, such as Quantum Electrodynamics. Making use of
the notion of charge class, an extension of the concept of superselection
sector, infrared problems are avoided by restricting the states to observables
localized in a light cone. The charge structure of a theory can be explored in
a systematic manner. The present analysis focuses on simple charges, thus
including the electric charge. It is shown that any such charge has a conjugate
charge. There is a meaningful concept of statistics: the corresponding charge
classes are either of Bose or of Fermi type. The family of simple charge
classes is in one--to--one correspondence with the irreducible unitary
representations of a compact Abelian group. Moreover, there is a meaningful
definition of covariant charge classes. Any such class determines a continuous
unitary representation of the Poincar\'e group or its covering group satisfying
the relativistic spectrum condition. The resulting particle aspects are also
briefly discussed.

Keywords:

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