Stochastic dark energy from inflationary quantum fluctuations

TL;DR

This paper proposes a model where inflationary quantum fluctuations of a light scalar field can generate dark energy, with the backreaction studied through a stochastic inflation formalism that predicts a testable effective equation of state.

Contribution

It introduces a novel approach to modeling dark energy via inflationary quantum fluctuations using stochastic inflation formalism, accounting for backreaction effects self-consistently.

Findings

Dark energy characterized by a distinct effective equation of state parameter.

The model's predictions are testable at the background level.

Backreaction effects are significant and can be incorporated self-consistently.

Abstract

We study the quantum backreaction from inflationary fluctuations of a very light, non-minimally coupled spectator scalar and show that it is a viable candiate for dark energy. The problem is solved by suitably adapting the formalism of stochastic inflation. This allows us to self-consistently account for the backreaction on the background expansion rate of the Universe where its effects are large. This framework is equivalent to that of semiclassical gravity in which matter vacuum fluctuations are included at the one loop level, but purely quantum gravitational fluctuations are neglected. Our results show that dark energy in our model can be characterized by a distinct effective equation of state parameter (as a function of redshift) which allows for testing of the model at the level of the background.