Scalar perturbations in deflationary cosmological models

TL;DR

This paper studies scalar density perturbations in early universe models that undergo accelerated expansion and naturally transition to standard cosmology, highlighting the role of primordial extended objects in setting cosmological scales.

Contribution

It introduces a geometric method for modeling deflationary cosmologies driven by primordial extended objects, avoiding fine-tuning for graceful exit.

Findings

Characteristic scales linked to primordial objects are selected.

Model aligns with string cosmology results.

Early accelerated expansion transitions smoothly to standard cosmology.

Abstract

We consider scalar perturbations of energy--density for a class of cosmological models where an early phase of accelerated expansion evolves, without any fine--tuning for graceful exit, towards the standard Friedman eras of observed universe. The geometric procedure which generates such models agrees with results for string cosmology since it works if dynamics is dominated by a primordial fluid of extended massive objects. The main result is that characteristic scales of cosmological interest, connected with the extension of such early objects, are selected.}