Cold plus hot dark matter cosmology in the light of solar and atmospheric neutrino oscillations

Abstract

We explore the implications of possible neutrino oscillations, as indicated by the solar and atmospheric neutrino experiments, for the cold plus hot dark matter scenario of large scale structure formation. We find that there are essentially three distinct schemes that can accommodate the oscillation data and which also allow for dark matter neutrinos. These include (i) three nearly degenerate (in mass) neutrinos, (ii) non-degenerate masses with ν τ in the eV range, and (iii) nearly degenerate ν µ − ν τ pair (in the eV range), with the additional possibility that the electron neutrino is cosmologically significant. The last two schemes invoke a 'sterile' neutrino which is light ( < ∼ eV). We discuss the implications of these schemes forν µ −ν e and ν µ − ν τ oscillation, and find that scheme (ii) in particular, predicts them to be in the observable range. As far as structure formation is concerned, we compare the one neutrino flavor case with a variety of other possibilities, including two and three degenerate neutrino flavors. We show, both analytically and numerically, the effects of these neutrino mass scenarios on the amplitude of cosmological density fluctuations. With a Hubble constant of 50 km s −1 Mpc −1 , a spectral index of unity, and Ω baryon = 0.05, the two and three flavor scenarios fit the observational data marginally better than the single flavor scheme. However, taking account of the uncertainties in these parameters, we show that it is premature to pick a clear winner.

The epoch of structure formation in blue mixed dark matter models

“…A further possibility is sharing the hot component between more than one massive neutrino species Pogosyan & Starobinsky 1995b;Babu, Schaefer & Shafi 1995). The subsequent variation of the neutrino freestreaming has been shown to decrease σ8 to an adequate level, without significantly affecting results at the galactic scale, which is relevant for DLAS.…”

Affleck-Dine baryogenesis after thermal inflation

“…As discussed in Section 2, we expect T f ∼ 1 to 10 GeV and M ∼ 10 10 to 10 12 GeV. Neutrino phenomenology [11,24] suggests m ν τ L ∼ 5 eV, m ν µL ∼ 10 …”

“…suitable for the mixed dark matter scenario for the formation of the large scale structure of the Universe [11]. The latter coupling ψH u H d does not have any good independent motivation, apart from the fact that it is possible.…”

Absorption of High‐Energy Gamma Rays by Interactions with Extragalactic Starlight Photons at High Redshifts and the High‐Energy Gamma‐Ray Background

“…The non-baryonic mixed dark matter model with a total Ω = 1 (Shafi & Stecker 1984) gave predictions for fluctuations in the cosmic background radiation (Schaefer, Shafi & Stecker 1989;Holtzman 1989) which were found to be in good agreement with the later COBE measurements. The best agreement appears to be found for ∼ 20% hot dark matter, of which massive neutrinos are the most likely candidates, and ∼ 80% cold dark matter (Pogosian & Starobinsky 1993Ma & Bertchinger 1994;Klypin, et al 1995;Primack, et al 1995;Liddle, et al 1996;Babu, Schaefer & Shafi 1996).…”