Cosmological Relaxation from Dark Fermion Production

Abstract

We consider the cosmological relaxation solution to the electroweak hierarchy problem using the fermion production as a dominant friction force. In our approach, neither super-Planckian field excursions nor a large number of e-folds arise, and scanning over thermal Higgs mass squared is avoided. The produced fermions from the relaxion source through the derivative coupling are SM-singlets, what we call dark fermions, and they can serve as the keV scale warm dark matter candidates.

Comments: 40 pages, 9 figures; small modifications in the appendix: comments on the static Universe limit added, brief discussion about the shutdown of the backraction added; version accepted for publication in JHEP