Probing the creatable character of perturbed Friedmann-Robertson-Walker universes

TL;DR

This paper investigates whether perturbed Friedmann-Robertson-Walker universes can have zero energy, momentum, and angular momentum, finding that closed universes are creatable while flat universes with standard inflation are not.

Contribution

It is the first study to analyze the creatable nature of perturbed FRW universes considering various perturbation spectra and inflationary conditions.

Findings

Closed perturbed universes are creatable.

Flat universes with standard inflation are not creatable.

Considerations on pre-inflationary scalar perturbations included.

Abstract

We discuss whether some perturbed Friedmann-Robertson-Walker (FRW) universes could be creatable, i. e., could have vanishing energy, linear momentum and angular momentum, as it could be expectable if the Universe arose as a quantum fluctuation. On account of previous results, the background is assumed to be either closed (with very small curvature) or flat. In the first case, fully arbitrary linear perturbations are considered; whereas in the flat case, it is assumed the existence of: (i) inflationary scalar perturbations, that is to say, Gaussian adiabatic scalar perturbations having an spectrum close to the Harrison-Zel'dovich one, and (ii) arbitrary tensor perturbations. We conclude that, any closed perturbed universe is creatable, and also that, irrespective of the spectrum and properties of the inflationary gravitational waves, perturbed flat FRW universes with standard inflation are not creatable. Some considerations on pre-inflationary scalar perturbations are also presented. The creatable character of perturbed FRW universes is studied, for the first time, in this paper.