Vacuum Choices and the Predictions of Inflation

TL;DR

This paper investigates how vacuum choice ambiguities in inflationary models with a cutoff affect predictions, showing that these uncertainties lead to oscillatory corrections in the power spectrum and exploring constraints via gravitational particle production.

Contribution

It introduces a parametrization of vacuum ambiguities in non-de Sitter inflation and analyzes their impact on the power spectrum and potential observational constraints.

Findings

Oscillatory corrections to the power spectrum proportional to Hubble over cutoff scale.

Vacuum ambiguities are linked to initial condition choices and universe expansion effects.

Gravitational particle production can constrain vacuum parameters.

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 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 generated power spectrum receives oscillatory corrections whose amplitude 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.