Quantum Cosmological Perturbations: Predictions and Observations

TL;DR

This paper analyzes the generic predictions of quantum cosmological perturbations during inflation, showing a minimum deviation in spectral index and linking hydrodynamical models to inflationary scenarios.

Contribution

It provides a model-independent analysis of inflationary perturbations using hydrodynamical approaches, establishing bounds on spectral index deviations and gravitational wave production.

Findings

Spectral index deviates from flat by at least 3%

Lower bound on gravitational wave amplitude derived

Hydrodynamical description relates to inflationary scenarios

Abstract

I consider the generic model independent predictions of the theory of quantum cosmological perturbations. To describe the stage of cosmic inflation, where these perturbations are amplified, the hydrodynamical approch is used. The inflationary stage is completely characterized by the deviation of the equation of state from cosmological constant which is a smooth function of the number of e-folds until the end of inflation. It is shown that in this case the spectral index should deviate from the flat one at least by 3 percent irrespective of any particular scenario. Given the value of the spectral index the lower bound on the amount of the gravitational waves produced is derived. Finally the relation between effective hydrodynamical description of inflation and inflationary scenarios is discussed.