Effects of sterile neutrinos on the ultrahigh-energy cosmic neutrino flux

We investigate the effect of sterile neutrinos that are nearly degenerate with active ones on the flux of ultrahigh-energy cosmic ray neutrinos at earth. This offers a way to probe neutrino oscillations in the mass-squared range 10−16 eV2≲δm2≲10−11 eV2 which maybe hard to detect by any other means. Taking into account the present experimental uncertainties of the active–active mixing angles and by allowing any values for the active–sterile mixing angles we find that the ratio of the electron and muon neutrino fluxes may change by −40% to 70% in comparison with the ratio in the absence of active–sterile mixing.