  We consider self-interacting, perturbative quantum field theory in a curved
spacetime background with a Killing vector field. We show that the action of
this spacetime symmetry on interacting field operators can be implemented by a
Noether charge which arises as a surface integral over the time-component of
the interacting Noether current-density associated with the Killing field. The
proof of this involves the demonstration of a corresponding set of Ward
identities. Our work is based on the perturbative construction by Brunetti and
Fredenhagen (Commun.Math.Phys. 208 (2000) 623-661) of self-interacting quantum
field theories in general globally hyperbolic spacetimes.
