Indecomposable semiinfinite string-localized positive energy matter and   "darkness"
  In the absence of interactions indecomposable positive energy quantum matter comes in form of three families of which the massless so called "infinite spin" family which appeared first in Wigner's famous 1939 work is (if mentioned at all) usually dismissed as "unphysical" but without indicating what principle (if at all) is being violated. Using novel methods which are particularly suited for problems of localization, it was shown that these representations cannot be generated by pointlike localized fields but rather require the introduction of string-like generators which are localized along semiinfinite spacelike strings. We argue that such objects can neither be registered in quasilocal Araki-Haag counters nor pair-produced from standard matter. Reviewing the mathematical status of Murphy's law in local quantum physics (everything which is not prohibited to couple does indeed couple) off and on shell, we are led to the result that perfect darkness is only possible in QFT with string-localized fields. PACS: 95.35+d, 11.10-z, 11.30Cp 
Bert Schroer