FEASIBILITY OF OBSERVING MECHANICAL EFFECTS OF COSMOLOGICAL NEUTRINOS

We reexamine mechanical effects of cosmological neutrinos, and the pos sibility of their detection. Classical and quantum-mechanical results are derived for the mean force on a spherical target mass due to neutr inos that are either extremely relativistic, nonrelativistic but unclu stered, or nonrelativistic and clustered; results are presented for Di rac and Majorana massive neutrinos. We find that there is no O(G(F)) m ean force, in agreement with earlier calculations. In addition, we dem onstrate that there are fluctuating forces O(G(F)(2)), which are more important than the mean force except on sufficiently long time scales that we evaluate case by case. Thus, fluctuations may act as a source of noise for any experiment seeking to detect the small, mean force du e to background neutrinos even if all other sources of noise can be el iminated. In addition, we show that the fluctuating forces on a pair o f nearby targets due to background neutrinos should be correlated, and that interference effects can lead to a short-range ''shadowing force '' between targets even in a perfectly isotropic background. Finally, the rates of phonon excitation both from the ground state and for a st ate with nonzero preexisting excitation are computed.