Decaying Vacuum Inflationary Cosmologies: A Complete Scenario Including Curvature Effects

TL;DR

This paper introduces a comprehensive class of nonsingular cosmological models with arbitrary curvature, driven by a time-varying vacuum energy, providing a natural transition from inflation to radiation and addressing the graceful exit problem.

Contribution

It presents a new class of cosmological models with dynamical vacuum energy that include curvature effects and naturally transition from inflation to radiation.

Findings

Models evolve between two de Sitter phases for all curvature values.

Universal transition from inflation to radiation phase.

Relic vacuum energy density ratio is approximately 10^123 when initial scale is Planckian.

Abstract

We propose a large class of nonsingular cosmologies of arbitrary spatial curvature whose cosmic history is determined by a primeval dynamical $\Lambda (t)$-term. For all values of the curvature, the models evolve between two extreme de Sitter phases driven by the relic time-varying vacuum energy density. The transition from inflation to the radiation phase is universal and points to a natural solution of the graceful exit problem regardless of the values of the curvature parameter. The flat case recovers the scenario recently discussed in the literature (Perico et al., Phys. Rev. D88, 063531, 2013). The early de Sitter phase is characterized by an arbitrary energy scale $H_I$ associated to the primeval vacuum energy density. If $H_I$ is fixed to be nearly the Planck scale, the ratio between the relic and the present observed vacuum energy density is $\rho_{vI}/\rho_{v0} \simeq 10^{123}$.