2 articles
Astrophysical and cosmological constraints on WISPs
Astrophysical and cosmological constraints on WISPs covers how stellar cooling, supernova 1987A, cosmic microwave background data, and black-hole superradiance bound axion-like particles, hidden photons, and other very light particles.
Dark radiation
Dark radiation is any component of the Universe's radiation energy density made of relativistic particles beyond photons and standard-model neutrinos, measured through the parameter N_eff.