Cosmological Consequences of a Variable Cosmological Constant Model

TL;DR

This paper proposes a dynamic dark energy model with a time-evolving cosmological constant, predicting both accelerated and decelerated phases, and offers a novel explanation for the small observed curvature of the universe.

Contribution

It introduces a variable cosmological constant model with a specific equation of state, providing insights into universe expansion phases and vacuum energy gravitation.

Findings

Model predicts both accelerated and decelerated expansion phases.

Universe age aligns with observational data.

Vacuum energy gravitates differently, explaining tiny curvature.

Abstract

We derive a model of dark energy which evolves with time via the scale factor. The equation of state $\omega=(1-2\alpha)/(1+2\alpha)$ is studied as a function of a parameter $\alpha$ introduced in this model. In addition to the recent accelerated expansion, the model predicts another decelerated phase. The age of the universe is found to be almost consistent with observation. In the limiting case, the cosmological constant model, we find that vacuum energy gravitates with a gravitational strength, different than Newton's constant. This enables degravitation of the vacuum energy which in turn produces the tiny observed curvature, rather than a 120 orders of magnitude larger value.