A background independent perturbative approach to quantum gravity

Quantum field theory on curved spacetime has recently achieved a satisfactory formulation in terms of a functor which associates globally hyperbolic spacetimes to algebras of observables. In this formulation a generally covariant construction of perturbative quantum field theory on generic backgrounds can be given. An attractive feature is the possibility to include dynamical variations of the spacetime metric. The requirement of background independence amounts to Ward identities which essentially are equivalent to the field equation for the metric field. As the theory is nonrenormalizable, it may be interpreted as an effective theory.