Cosmological Perturbations from a New Approach to Inflation

TL;DR

This paper explores a novel inflationary model starting from a lingering universe state, examining its stability, perturbations, and observational implications, offering an alternative to eternal and cyclic inflation scenarios.

Contribution

It introduces a new inflationary paradigm based on a lingering universe state, analyzing perturbations and stability, and contrasting it with existing models.

Findings

Perturbations affect the stability of the lingering phase.

The model provides distinct observational signatures.

Addresses transition mechanisms to standard inflation.

Abstract

In a previous paper we proposed a new approach to the beginning of inflation -- a lingering universe. The universe begins in a lingering state with a nearly vanishing Hubble parameter. This calls into question the absolute age of the universe, as the Hubble time can be nearly infinite. It also provides promise for addressing the initial singularity of inflation and issues with quantum field theory in de Sitter space-time. Such models arise in classical cosmologies with non-vanishing spatial curvature (inspired by PLANCK 2018 data), and independently by models that arise in string cosmology. In this paper, we consider the importance of cosmological perturbations for the stability of the lingering phase and how this influences cosmological observations. Our goal is to establish observables in this new paradigm for the origin of inflation which is in contrast to eternal inflation and cyclic cosmologies. We also address questions of stability and the transition to inflation.