Cosmological signatures of interacting neutrinos

Nicole F. Bell, Elena Pierpaoli, and Kris Sigurdson
Phys. Rev. D 73, 063523 – Published 22 March 2006

Abstract

We investigate signatures of neutrino scattering in the cosmic microwave background (CMB) and matter power spectra, and the extent to which present cosmological data can distinguish between a free-streaming or tightly coupled fluid of neutrinos. If neutrinos have strong nonstandard interactions, for example, through the coupling of neutrinos to a light boson, they may be kept in equilibrium until late times. We show how the power spectra for these models differ from more conventional neutrino scenarios, and use CMB and large scale structure data to constrain these models. CMB polarization data improves the constraints on the number of massless neutrinos, while the Lyman-α power spectrum improves the limits on the neutrino mass. Neutrino mass limits depend strongly on whether some or all of the neutrino species interact and annihilate. The present data can accommodate a number of tightly coupled relativistic degrees of freedom, and none of the interacting-neutrino scenarios considered are ruled out by current data—although considerations regarding the age of the Universe disfavor a model with three annihilating neutrinos with very large neutrino masses.

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  • Received 16 November 2005

DOI:https://doi.org/10.1103/PhysRevD.73.063523

©2006 American Physical Society

Authors & Affiliations

Nicole F. Bell1,2,*, Elena Pierpaoli2,†, and Kris Sigurdson2,3,‡

  • 1Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125, USA
  • 2Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91125, USA
  • 3School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey 08540, USA

  • *Electronic address: nfb@caltech.edu
  • Electronic address: pierpa@caltech.edu
  • Hubble Fellow; Electronic address: krs@ias.edu

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Issue

Vol. 73, Iss. 6 — 15 March 2006

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