Dark Energy Radiation

TL;DR

This paper explores the possibility that evolving dark energy could be dominated by dark radiation, which might significantly influence cosmic expansion and be detectable through cosmological and laboratory experiments.

Contribution

It introduces models where dark energy's dynamical component includes dark radiation, linking it to observable effects and potential laboratory detection.

Findings

Dark radiation could have up to 10^4 times the energy density of CMB.

Cosmological expansion history is sensitive to dark radiation temperature.

Dark radiation may be directly detectable in laboratory experiments.

Abstract

We show that if dark energy evolves in time, its dynamical component could be dominated by a bath of dark radiation. Within current constraints this radiation could have up to $\sim 10^4$ times more energy density than the cosmic microwave background. We demonstrate particular models in which a rolling scalar field generates different forms of dark radiation such as hidden photons, milli-charged particles and even Standard Model neutrinos. We find the leading effect on the late-time cosmological expansion history depends on a single parameter beyond $\Lambda$CDM, namely the temperature of the dark radiation today. Cosmological observations of this modified expansion rate could provide a striking signature of this scenario. The dark radiation itself could even be directly detectable in laboratory experiments, suggesting a broader experimental program into the nature of dark energy.