%0 Journal Article
%T Extrinsic Time in Quantum Cosmology
%A S. C. Beluardi
%A Rafael Ferraro
%J Physics
%D 1994
%I arXiv
%R 10.1103/PhysRevD.52.1963
%X An extrinsic time is identified in most isotropic and homogeneous cosmological models by matching them with the ideal clock - a parametrized system whose only "degree of freedom" is time -. Once this matching is established, the cosmological models are quantized in the same way as the ideal clock. The space of solutions of the Wheeler-DeWitt equation is turned out into a Hilbert space by inserting a time dependent operator in the inner product, yielding a unitary theory equivalent to the phase space reduced theory.
%U http://arxiv.org/abs/gr-qc/9409032v2