Decoherence in quantum cosmology at the onset of inflation
Abstract
We calculate the reduced density matrix for the inflaton field in a model of chaotic inflation by tracing out degrees of freedom corresponding to various bosonic fields. Apart from the standard decoherence factor there also arises a contribution from the Euclidean effective action of quantum fields. We regularise the ultraviolet divergences in the decoherence factor. Dimensional regularisation does not work because it would lead to a density matrix which does not define a bounded operator. A conformal redefinition of the environmental fields leads to a bounded density matrix. This redefinition is essentially fixed by the requirement that decoherence be absent for vanishing particle creation. Offdiagonal elements of the reduced density matrix become negligibly small for nonconformally invariant fields, so that due to bosonic fields the Universe can acquire classical properties near the onset of inflation.
 Publication:

Nuclear Physics B
 Pub Date:
 June 1999
 DOI:
 10.1016/S05503213(99)002084
 arXiv:
 arXiv:grqc/9812043
 Bibcode:
 1999NuPhB.551..374B
 Keywords:

 QUANTUM COSMOLOGY;
 INFLATION;
 QUANTUMTOCLASSICAL TRANSITION;
 General Relativity and Quantum Cosmology
 EPrint:
 LATEX, 26 pages