Complex velocity transformations and the Bisognano-Wichmann theorem for quantum fields acting on Krein spaces

It is proven that in indefinite metric quantum field theory there exists a dense set of analytic vectors for the generator of the one parameter group of x0-x1 velocity transformations. This makes it possible to define complex velocity transformations also for the indefinite metric case. In combination with the results of Bros, Epstein, and Moschella [Commun. Math. Phys. 196, 535-570 (1998)], proving Bisognano-Wichmann (BW) analyticity within the linear program, one then obtains a suitable generalization of the BW theorem for local, relativistic quantum fields acting on Krein spaces ('quantum fields with indefinite metric')