Wojciech Dybalski on June 22, 2018
We advance superselection theory of pure states on a C*-algebra beyond the conventional DHR setting. First, we canonically define conjugate and second-conjugate classes of such states w.r.t. a given reference `vacuum state’ and a `background automorphism’. Next, we identify a subset of backgrounds which take distinct sectors into one (second-)conjugate
class. We show that the Kraus-Polley-Reents infravacuum automorphisms fit into our framework and discuss consequences for the infrared problem in QED. Comparison with the approach of Kunhardt and with the concept of `charge classes’ of Buchholz and Roberts will also be given.