Related papers: Are cosmological neutrinos free-streaming?
Several anomalies in neutrino oscillation experiments point to the existence of a $\sim 1\,$eV sterile neutrino $\nu_s$ mixing with $\nu_e$ at the level of $U_{e4}\cong 0.1$, but such a neutrino is strongly disfavored by constraints on…
New physics in the neutrino sector might be necessary to address anomalies between different neutrino oscillation experiments. Intriguingly, it also offers a possible solution to the discrepant cosmological measurements of $H_0$ and…
We point out that in scenarios with a low reheating temperature $T_R << 100$ MeV at the end of (the last episode of) inflation or entropy production, the abundance of sterile neutrinos becomes largely independent of their coupling to active…
We investigate a model where neutrinos are strongly coupled to a new, light scalar field. In this model neutrinos annihilate as soon as they become non-relativistic in the early universe, and a non-zero neutrino mass has a marginal effect…
Three relativistic particles in addition to the photon are detected in the cosmic microwave background (CMB). In the standard model of cosmology, these are interpreted as the three neutrino species. However, at the time of CMB-decoupling,…
In several classes of particle physics models -- ranging from the classical Majoron models, to the more recent scenarios of late neutrino masses or Mass-Varying Neutrinos -- one or more of the neutrinos are postulated to couple to a new…
We study the evolution of linear density fluctuations of free-streaming massive neutrinos at redshift of z<1000, with an explicit justification on the use of a fluid approximation. We solve the collisionless Boltzmann equation in an…
Nonstandard self-interactions can alter the evolution of cosmological neutrinos, mainly by damping free streaming, which should leave traces in cosmological observables. Although overall effects are opposite to those produced by neutrino…
Future cosmological data may be sensitive to the effects of a finite sum of neutrino masses even as small as ~0.06 eV, the lower limit guaranteed by neutrino oscillation experiments. We show that a cosmological detection of neutrino mass at…
Standard cosmology predicts that prior to matter-radiation equality about 41% of the energy density was in free-streaming neutrinos. In many beyond Standard Model scenarios, however, the amount and free-streaming nature of this component is…
It is commonly assumed that the cosmological and astrophysical bounds on the mixings of sterile with active neutrinos are much more stringent than those obtained from laboratory measurements. We point out that in scenarios with a very low…
Some cosmic microwave background (CMB) data allow a cosmological scenario in which the free streaming of neutrinos is delayed until close to matter-radiation equality. Interestingly, recent analyses have revealed that large-scale structure…
At present, the strongest upper limit on $\sum m_{\nu}$, the sum of neutrino masses, is from cosmological measurements. However, this bound assumes that the neutrinos are stable on cosmological timescales, and is not valid if the neutrino…
We study the effects induced by new neutral fermions below their mass threshold, due to their possible mixing with the standard neutrinos. We use as experimental constraints the recent results on lepton universality, together with the…
A calculation of neutrino decoupling in the early Universe, including full Fermi-Dirac statistics and electron mass dependence in the weak reaction rates, is presented. We find that after decoupling, the electron neutrinos contribute 0.83\%…
The light neutrino masses are at present most stringently constraint via cosmological probes. In particular the Planck collaboration reports $ \sum m_\nu \leq 0.12\,\mathrm{eV}$ at $95\%$ CL within the standard cosmological model. This is…
In this paper we study the effect of cosmic neutrino decoupling on the spectrum of cosmological gravitational waves (GWs). At temperatures T>>1 MeV, neutrinos constitute a perfect fluid and do not hinder GW propagation, while for T<<1 MeV…
We consider relatively heavy neutrinos $\nu_H$, mostly contributing to a sterile state $\nu_s$, with mass in the range 10 MeV $\lesssim m_s \lesssim m_{\pi} \sim 135$ MeV, which are thermally produced in the early universe in collisional…
A cosmological scenario in which the onset of neutrino free streaming in the early Universe is delayed until close to the epoch of matter-radiation equality has been shown to provide a good fit to some cosmic microwave background (CMB)…
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}…