Cosmology of Gravi-Axions
Abstract
We show how a mass term for gravitational axions (''gravi-axions'') with a Chern-Simons coupling to gravity can naturally arise due to non-perturbative contributions from Euclidean wormholes, breaking the continuous shift symmetry of the standard theory. The induced mass can be generated in a cosmologically relevant range to be the dark matter or dark energy of the universe for a reasonable and well-motivated range of the symmetry breaking scale. Upon generating the gravi-axion mass term, we discuss the cosmology of the theory. We find that the gravi-axion can be produced to be the dominant dark matter component via misalignment or gravitational particle production, and that in a different regime, the gravi-axion can act as dynamical dark energy. We discuss gravi-axion decay into gravitons as a potential observational window for this theory. Finally, we find that, for late-time, astrophysical compact objects, cosmologically relevant gravi-axions behave as minimally-coupled, massive scalar fields.
Cite
@article{arxiv.2512.00154,
title = {Cosmology of Gravi-Axions},
author = {Stephon Alexander and Gregory Gabadadze and Leah Jenks and Nicolás Yunes},
journal= {arXiv preprint arXiv:2512.00154},
year = {2025}
}
Comments
16 pages, 5 figures