Abstract
In the presence of a short-distance cutoff, the choice of a vacuum state in an inflating, non-de Sitter universe is unavoidably ambiguous. The ambiguity is related to the time at which initial conditions for the mode functions are specified and to the way in which the expansion of the universe affects those initial conditions. In this paper we study the imprint of these uncertainties on the predictions of inflation. We parametrize the most general set of possible vacuum initial conditions by two phenomenological variables. We find that the power spectrum generated receives an oscillatory correction, the amplitude of which is proportional to the Hubble parameter over the cutoff scale. In order to further constrain the phenomenological parameters that characterize the vacuum definition, we study gravitational particle production during different cosmological epochs.
Highlights
Inflation [1] causally explains the origin of the superhorizon density perturbations that seed the structures we observe in the universe
Causality within the Hubble radius naturally allows us to determine their initial amplitude by postulating that perturbations start in their vacuum state
In de Sitter space there exists a concrete set of vacuum states invariant under the symmetry group of the spacetime
Summary
Inflation [1] causally explains the origin of the superhorizon density perturbations that seed the structures we observe in the universe. In the presence of a cutoff, in order to minimize the ambiguity related to the expansion of the universe, and in order to avoid the region of unknown physics, the best one can do is to define the vacuum at the time the physical length λ of the mode equals the fundamental length scale of the theory, Λ−1 [8]. The conventional predictions of inflation get modified due to the finite effects of the expansion of the universe [9] These corrections can be expanded as a series in H/Λ. Let us stress though, that the corrections we are talking about have little to do with trans-Planckian physics (see [10] for a review) Rather, they arise from the uncertainties related to the definition of vacuum in an expanding universe. Instead of relying on theoretical arguments to single out the vacuum that was realized during inflation, we shall rely on observations to put constraints on possibly realized vacua
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
