Dark energy from quantum gravity discreteness

TL;DR

This paper proposes that quantum gravity's fundamental discreteness causes tiny violations of energy-momentum conservation, which can manifest as an effective dark energy component explaining the observed cosmological constant.

Contribution

It introduces a novel mechanism linking quantum gravity discreteness to dark energy through energy diffusion effects in cosmology.

Findings

Estimates of the effect match the observed cosmological constant magnitude.

Discreteness-induced energy diffusion can produce dark energy without fine tuning.

The model respects Lorentz invariance constraints at low energies.

Abstract

We argue that discreteness at the Planck scale (naturally expected to arise from quantum gravity) might manifest in the form of minute violations of energy-momentum conservation of the matter degrees of freedom when described in terms of (idealized) smooth fields on a smooth spacetime. In the context of applications to cosmology such `energy diffusion' from the low energy matter degrees of freedom to the discrete structures underlying spacetime leads to the emergence of an effective dark energy term in Einstein's equations. We estimate this effect using a (relational) hypothesis about the materialization of discreteness in quantum gravity which is motivated by the strict observational constraints supporting the validity of Lorentz invariance at low energies. The predictions coming from simple dimensional analysis yield a cosmological constant of the order of magnitude of the observed value without fine tuning.