A possible signature of cosmic neutrino decoupling in the nHz region of the spectrum of primordial gravitational waves

Massimiliano Lattanzi, Riccardo Benini, Giovanni Montani

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In this paper we study the effect of cosmic neutrino decoupling on the spectrum of cosmological gravitational waves (GWs). At temperatures T ≫ 1MeV, neutrinos constitute a perfect fluid and do not hinder GW propagation, while for T ≪ 1MeV they free-stream and have an effective viscosity that damps cosmological GWs by a constant amount. In the intermediate regime, corresponding to neutrino decoupling, the damping is frequency dependent. GWs entering the horizon during neutrino decoupling have a frequency f ∼ 1 nHz, corresponding to a frequency region that will be probed by pulsar timing arrays (PTAs). In particular, we show how neutrino decoupling induces a spectral feature in the spectrum of cosmological GWs just below 1 nHz. We briefly discuss the conditions for detection of this feature and conclude that it is unlikely to be observed by PTAs. © 2010 IOP Publishing Ltd.
Original languageEnglish
Article number194008
Pages (from-to)-
JournalClassical and Quantum Gravity
Issue number19
Publication statusPublished - 7 Oct 2010
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

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