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General Relativity and Quantum Cosmology, gr-qc,High Energy Physics - Theory, hep-th
Abstract:
We investigate the implications for cosmology of a phenomenological quantum
gravity approach based on thermodynamics. We analyze in detail the
corresponding primordial power spectrum. The considered modified cosmological
scenario has similarities with Loop Quantum Cosmology. Actually, one recovers
the same effective background dynamics by fixing the value of the free
parameter of the modified approach. In particular, the background experiences a
bounce that solves the initial singularity. Adopting background-dependent
equations for the primordial perturbations like those derived in General
Relativity, the studied model can be considered a generalization of the dressed
metric formalism in Loop Quantum Cosmology. We focus our discussion on the
spectrum of tensor perturbations. For these perturbations, we compute the exact
form of the background-dependent effective mass that affects their propagation.
Since there are background regimes in the modified cosmology that are far away
from slow-roll inflation, we do not have at our disposal a privileged vacuum
like the Bunch-Davies state. We then select the state of the perturbations by a
recently proposed criterion that removes unwanted oscillations in the power
spectrum. Finally, we numerically compute the spectrum of this vacuum and
compare it with other spectra obtained in the literature, especially with one
corresponding to an alternative quantization prescription in Loop Quantum
Cosmology (called the hybrid prescription).
