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On the interaction between thermalized neutrinos and cosmological gravitational waves above the electroweak unification scale

Massimiliano Lattanzi·Giovanni Montani
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Abstract

We investigate the interaction between the cosmological relic neutrinos, and primordial gravitational waves entering the horizon before the electroweak phase transition, corresponding to observable frequencies today nu_0 <= 10^-5 Hz. We give an analytic formula for the traceless transverse part of the anisotropic stress tensor, due to weakly interacting neutrinos, and derive an integro-differential equation describing the propagation of cosmological gravitational waves at these conditions. We find that this leads to a decrease of the wave intensity in the frequency region accessible to the LISA space interferometer, that is at the present the most promising way to obtain a direct detection of a cosmological gravitational wave. The absorbed intensity does not depend neither on the perturbation wavelength, nor on the details of neutrino interactions, and is affected only by the neutrino fraction f_nu. The transmitted intensity amounts to 88% for the standard value f_nu=0.40523. An approximate formula for non-standard values of f_nu is given.

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Massimiliano Lattanzi, Giovanni Montani. 2005-08-16. On the interaction between thermalized neutrinos and cosmological gravitational waves above the electroweak unification scale. https://doi.org/10.1142/s0217732305018827

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