Search

We present a consistent framework to set limits on properties of light sterile neutrinos coupled to all three active neutrinos using a combination of the latest cosmological data and terrestrial measurements from oscillations, β-decay, and neutrinoless double-β-decay (0νββ) experiments. We directly constrain the full 3+1 active-sterile mixing matrix elements |Uα4|², with α∈(e,μ,τ), and the mass-squared splitting Δm²41≡m24-m21. We find that results for a 3+1 case differ from previously studied 1+1 scenarios where the sterile is coupled to only one of the neutrinos, which is largely explained by parameter space volume effects. Limits on the mass splitting and the mixing matrix elements are currently dominated by the cosmological datasets. The exact results are slightly prior dependent, but we reliably find all matrix elements to be constrained below |Uα4|²≲10-3. Short-baseline neutrino oscillation hints in favor of eV-scale sterile neutrinos are in serious tension with these bounds, irrespective of prior assumptions. We also translate the bounds from the cosmological analysis into constraints on the parameters probed by laboratory searches, such as mβ or mββ, the effective mass parameters probed by β-decay and 0νββ searches, respectively. When allowing for mixing with a light sterile neutrino, cosmology leads to upper bounds of mβ<0.09 eV and mββ<0.07 eV at 95% CL, more stringent than the limits from current laboratory experiments. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are astrophysical transients of currently unknown origin, and so far several events have been detected at extragalactic distances. The dispersion measure (DM) of the radio signal is a probe of the integrated electron density along the line of sight and therefore allows to map the electron distribution within the large-scale structure. Since a fraction of electrons get expelled from galaxies by feedback, they are anticorrelated with halos at large scales and hence the angular DM correlations show a scale-dependent bias caused by primordial non-Gaussianity. Although the signal is weaker than in other probes like galaxy clustering, FRBs can potentially probe considerably larger volumes. We show that while studying the FRB clustering signal requires very large samples, correlations in the DM are cosmic-variance limited on large angular scales with only ~ 1 0 3 - 4 events. A tomographic analysis of the angular DM correlation function can constrain the local primordial bispectrum shape parameter f NL to a precision down to f NL ~ O (1) depending on assumptions about the FRB redshift distribution and the astrophysical feedback on large scales. This makes FRBs a competitive probe to constrain inflationary physics. [ABSTRACT FROM AUTHOR]