Authors: Daniel G Figueroa Tuukka Meriniemi
Publish Date: 2013/10/16
Volume: 2013, Issue: 10, Pages: 101-
Abstract
Outofequilibrium fermions can be created in the early Universe by nonperturbative parametric effects both at preheating or during the thermal era An anisotropic stress is developed in the fermion distribution acting as a source of a stochastic background of gravitational waves GW We derive a general formalism to calculate the spectrum of GW produced by an ensemble of fermions which we apply to a variety of scenarios after inflation We discuss in detail the regularization of the source ie of the unequaltimecorrelator of the fermions’ transversetraceless anisotropic stress We discuss how the GW spectrum builds up in time and present a simple parametrization of its final amplitude and peak frequency We find that fermions may generate a GW background with a significant amplitude at very high frequencies similarly to the case of preheating with scalar fields A detection of this GW background would shed light on the physics of the very early Universe but new technology at high frequencies is required beyond the range accessible to currently planned detectors
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