Axion Poltergeist
arXiv:2305.14242 · doi:10.1103/PhysRevD.108.L081303
Abstract
Rotations of axion fields in the early universe can produce dark matter and the matter-antimatter asymmetry of the universe. We point out that the rotation can generate an observable amount of a stochastic gravitational-wave (GW) background. It can be doubly enhanced in a class of models in which the equation of state of the rotations rapidly changes from a non-relativistic matter-like one to a kination-like one by 1) the so-called poltergeist mechanism and 2) slower redshift of GWs compared to the axion kination fluid. In supersymmetric UV completion, future GW observations can probe the supersymmetry-breaking scale up to GeV even if the axion does not directly couple to the Standard Model fields.
7 pages, 4 figures (Supplemental Material: 13 pages, 3 figures), v2: version published in PRD letter (except for the title). minor revision