http://arxiv.org/abs/1602.08416
We treat quantum creation of gravitons by small scale factor oscillations around the average of an expanding universe. Such oscillations are predicted both by modified gravity theories with a term proportional to the square of the Ricci scalar in the gravitational action, and by semiclassical gravity in which a renormalized expectation value of a quantum matter stress tensor is the source of gravity. A perturbative method due to Birrell and Davies involving an expansion in a conformal coupling parameter is used to calculate the number density and energy density of the created gravitons. Cosmological constraints on the present graviton energy density are discussed, which indicate an upper bound of the order of $4\%$ of the total mass-energy density of the universe. This constraint leads to an upper bound on the dimensionless amplitude of the oscillations. We also discuss decoherence of quantum systems produced by the spacetime geometry fluctuations due to such a graviton bath, and find a lower bound on the decoherence time resulting from this process.
E. Schiappacasse and L. Ford
Mon, 29 Feb 16
10/46
Comments: 17 pages, 2 figures
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