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arXiv · 1010.3849

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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Abstract

In this paper we study the effect of cosmic neutrino decoupling on the spectrum of cosmological gravitational waves (GWs). At temperatures T>>1 MeV, neutrinos constitute a perfect fluid and do not hinder GW propagation, while for T<<1 MeV 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 a detection of this feature and conclude that it is unlikely to be observed by PTAs.

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Massimiliano Lattanzi, Riccardo Benini, Giovanni Montani. 2011-03-11. A possible signature of cosmic neutrino decoupling in the nHz region of the spectrum of primordial gravitational waves. https://doi.org/10.1088/0264-9381%2F27%2F19%2F194008

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