Time-Varying Cosmological Term: Emergence and Fate of a FRW Universe

TL;DR

This paper explores a model where a time-varying cosmological constant influences universe evolution, leading to matter emergence, potential acceleration, and a novel dark energy-dominated singular state.

Contribution

It introduces a dynamic cosmological term model where Lambda decays and then increases, affecting matter creation, universe expansion, and the emergence of a new gravitational singularity.

Findings

Universe starts in a de Sitter phase and evolves towards FRW regime.

Decaying Lambda leads to matter emergence from an initially empty universe.

Increasing Lambda causes accelerated expansion towards a dark energy-dominated singularity.

Abstract

A time-varying cosmological "constant" Lambda is consistent with Einstein's equation, provided matter and/or radiation is created or destroyed to compensate for it. Supposing an empty primordial universe endowed with a very large cosmological term, matter will emerge gradually as Lambda decays. Provided only radiation or ultrarelativistic matter is initially created, the universe starts in a nearly de Sitter phase, which evolves towards a FRW regime as expansion proceeds. If, at some cosmological time, the cosmological term begins increasing again, as presently observed, expansion will accelerate and matter and/or radiation will be transformed back into dark energy. It is shown that such accelerated expansion is a route towards a new kind of gravitational singular state, characterized by an empty, conformally transitive spacetime in which all energy is dark.