Dark energy as the weight of violating energy conservation

TL;DR

This paper explores how violations of energy conservation in certain gravity theories could explain dark energy, linking quantum mechanics modifications and quantum gravity models to cosmological effects.

Contribution

It proposes a framework where energy non-conservation leads to an effective cosmological constant within unimodular gravity, connecting quantum effects to dark energy.

Findings

Energy non-conservation can produce an effective cosmological constant.

Quantum gravity effects at the Planck scale may influence cosmological dynamics.

Locally negligible phenomena can have significant cosmological implications.

Abstract

In this letter, we consider the possibility of reconciling metric theories of gravitation with violation of the conservation of energy-momentum. Under some circumstances, this can be achieved in the context of unimodular gravity, and it leads to the emergence of an effective cosmological constant in Einstein's equation. We specifically investigate two potential sources of energy non-conservation ---non-unitary modifications of quantum mechanics, and phenomenological models motivated by quantum gravity theories with spacetime discreteness at the Planck scale--- and show that such locally negligible phenomena can nevertheless become relevant at the cosmological scale.