Sterile neutrino dark matter from generalized CPT-symmetric early-Universe cosmologies

We generalize gravitational particle production in a radiation-dominated CPT-symmetric universe to nonstandard but also CPT-symmetric early-Universe cosmologies. We calculate the mass of a right-handed sterile neutrino needed for it to be the cosmological dark matter. Since generically sterile neutrinos mix with the standard model active neutrinos, we use state-of-the-art tools to compute the expected spectrum of gamma rays and high-energy active neutrinos from ultraheavy sterile neutrino dark matter decay. We demonstrate that the sterile neutrinos are never in thermal equilibrium in the early Universe. We show that very high-energy Cherenkov telescopes might detect a signal for sterile neutrino lifetimes up to around 10(27) s, while a signal in high-energy neutrino telescopes such as IceCube could be detectable for lifetimes up to 10(30) s, offering a better chance of detection across a vast landscape of possible masses.

Automated summary

The study generalizes the production of gravitational particles in a radiation-dominated, CPT-symmetric universe to nonstandard but also CPT-symmetric early-Universe cosmologies. Calculations were made to determine the necessary mass for a right-handed sterile neutrino to be cosmological dark matter. Additionally, state-of-the-art tools were utilized to compute the expected spectra of gamma rays and high-energy active neutrinos resulting from the decay of ultraheavy sterile neutrino dark matter. The research shows that the sterile neutrinos were never in thermal equilibrium in the early Universe and discusses the potential detection of signals for varying sterile neutrino lifetimes.