Cosmological Tests of the Hypothesis of Dark Matter as Bound Neutrinos

Abstract

A modest extension of the Standard Model allows a family-specific, feeble form of SU(3) that causes rapid binding of neutrinos at neutrino decoupling. These bound neutrinos become nonrelativistic well before recombination. Neutrinos are bound when all three neutrino flavors are present at densities expected in the early universe. Consistency is examined against observationally-inferred data, including free-streaming lengths, dark matter interaction rates, neutrinos from SN1987A, big-bang nucleosynthesis, and the cosmic microwave background. Consistency with galactic haloes and halo interactions was studied in a companion paper. The theory yields a ratio of dark matter density to neutrino density of 147, calculated in two different ways, agreeing with the current value of 158 assuming the sum of the masses of neutrino mass eigenstates is 0.07 eV/c2. This yields a ratio of dark matter to total matter of 83.2% with a relative uncertainty of at least ±8%. A free-streaming length of about 1 kpc is obtained for hard-sphere self-scattering, and about 115 kpc for 1/r-potential self-scattering, where r is the particle separation. A BBN analysis agrees with observationally-inferred abundances of He and Li, but not the latest deuterium measurements. The latter disagreement is the only identified potential inconsistency with current cosmological measurements. Both the standard SU(3) adapted to the neutrino family and a modest extension of SU(3) give good agreement with most observations. The extension provides a means to estimate dark matter parameters whereas the standard SU(3) does not. This explanation for dark matter does not require any new fundamental particles or forces.