title: Dark Energy from Violation of Energy Conservation.
abstract: In this Letter, we consider the possibility of reconciling metric theories of gravitation with a 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 nonconservation-nonunitary 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.
authors.affiliation: Aix Marseille Univ, Université de Toulon, CNRS, CPT, Marseille, France.
authors.forename: Thibaut
authors.initials: T
authors.lastname: Josset
authors.affiliation: Aix Marseille Univ, Université de Toulon, CNRS, CPT, Marseille, France.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Perez
authors.affiliation: Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, México D.F. 04510, México.
authors.forename: Daniel
authors.initials: D
authors.lastname: Sudarsky