The Analysis of Time-Space Translations in Quantum Fields
  I discuss the indefinite metrical structure of the time-space translations as realized in the indefinite inner products for relativistic quantum fields, familiar in the example of quantum gauge fields. The arising indefinite unitary nondiagonalizable representations of the translations suggest as the positive unitarity condition for the probability interpretable positive definite asymptotic particle state space the requirement of a vanishing nilpotent part in the time-space translations realization. A trivial Becchi-Rouet-Stora charge (classical gauge invariance) for the asymptotics in quantum gauge theories can be interpreted as one special case of this general principle - the asymptotic projection to the eigenstates of the time-space translations. 
Heinrich Saller