SINGULARITIES IN A SCALAR FIELD QUANTUM COSMOLOGY

The quantum theory of a spatially flat Friedmann-Robertson-Walker univ erse with a massless scalar field as the source is further investigate d. The classical model is singular and in the framework of a genuine c anonical quantization (Arnowitt-Deser-Misner formalism) a discussion i s made of the cosmic evolution, particularly of the quantum gravitatio nal collapse problem. It is shown that in a matter-time gauge such tha t time is identified with the scalar field the classical model is sing ular either at t = -infinity or at t = +infinity, but the quantum mode l is nonsingular. The latter behavior disproves a conjecture according to which quantum cosmological singularities are predetermined on the classical level by the choice of time.