Year: 2026
Type: preprint
Abstract: We propose a model in which the observed cosmic microwave background birefringence arises from the interaction of photons with a stiff ($w=1$) pseudo-scalar field that today contributes a subdominant fraction of the total energy density, distinct from both dark matter and dark energy. Big Bang Nucleosynthesis constrains the cosmological density of the stiff field, leading to a lower bound for its coupling with photons, $g_{ϕγ} > 8.9 \times 10^{-14}\,\mathrm{GeV}^{-1}$. Photon conversion in cluster-hosted quasars sets an upper bound, $g_{ϕγ} < 5.0 \times 10^{-13}\,\mathrm{GeV}^{-1}$. Therefore, there is a narrow window for the discovery of this cosmological component that can be explored in the forthcoming years with astrophysical axion searches. Moreover, we show that this scenario leads to gravitational-wave signals that can be tested with planned experiments.
Source: arXiv (Cornell University)
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G231133531, G972786147
OpenAlex ID: W7223152327