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Structure formation with strongly interacting neutrinos—implications for the cosmological neutrino mass bound

Steen Hannestad

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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 on the matter power spectrum. However, the angular power spectrum of the cosmic microwave background (CMB) is changed significantly because the strongly interacting fluid of neutrinos and scalars does not experience any anisotropic stress. Such models are strongly disfavoured by current observations. Interestingly, this leads to the conclusion that the relativistic energy density around the epoch of recombination must be in the form of very weakly interacting particles. This conclusion is independent of the specific interaction model.


Keywords

CMBR theory

neutrino properties

cosmological neutrinos

power spectrum

 

E-print Number: astro-ph/0411475

Cited: by |

Refers: to

PACS

12.15.Ff Quark and lepton masses and mixing

13.15.+g Neutrino interactions

12.10.Dm Unified theories and models of strong and electroweak interactions

Subjects

Particle physics and field theory

Dates

Issue 02 (February 2005)

Received 19 November 2004, accepted for publication 17 January 2005

Published 24 February 2005



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