Stochastic gravitational waves from spin-3/2 fields

Stochastic gravitational waves can be produced during the preheating when out-of-equilibrium particles are produced with an anisotropic stress tensor. We discuss the case where these particles carry spin 3/2. We compute the spectrum of the gravitational waves generated by the transverse and longitudinal components. We find a different scaling of the spectrum near the peak and the longitudinal components lead to an enhancement when compared to spin-1/2 fermions with Yukawa couplings. We note, as expected, that the corresponding typical frequency is too high for the current observation and calls for ultrahigh frequency gravitational wave detectors in the future.