Effective action in quantum gravity

It is argued that the effective action theory may be regarded as a phenomenological theory describing a certain class of measurements irrespective of the nature of fundamental quantum objects. The effective action in quantum field theory is discussed in detail and used as a guide. A connection between the effective field and observables is established. The approach is applied to the gravitational collapse problem. A procedure for building a basis of non-local gravitational invariants is described and a result for the vacuum radiation in a spherically symmetric in-state is presented. A conclusion about breakdown of measurements at the Planck scale is revised.