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Cosmological Consequences of an Unstable Heavy Neutrino
Published online by Cambridge University Press: 04 August 2017
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In a recent paper Simpson has reported evidence for a heavy neutrino of about 17.1 kev mass. Cosmological bounds on stable neutrino species imply that this neutrino [νH] must be unstable. The most likely decay mode νH→νL+f where νL is a light neutrino and f is a scalar boson leads to a cosmological scenario which is quite different from the conventional picture. In this scenario universe becomes matter dominated at a redshift of z ∼ 107 and becomes radiation dominated [by the decay product νL of νH] at z ∼ 310. The kinematic constraints on the lifetime of νH do not lead to any contradictions. On the other hand, growth of baryonic perturbations is severely limited in this model due to two reasons: (i) virtually no growth can take place in the radiation dominated region z ≤ 310. (ii) Decay of νH is likely to disrupt and smoothen out past growth by a large factor. It is doubtful whether a simple way out of this difficulty exists.
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- Copyright © Reidel 1987