Physical review letters | 2021
Einstein-Cartan Portal to Dark Matter.
Abstract
It is well known since the works of Utiyama and Kibble that the gravitational force can be obtained by gauging the PoincarĂ© group, which puts gravity on the same footing as the standard model fields. The resulting theory-Einstein-Cartan gravity-inevitably contains four-fermion and scalar-fermion interactions that originate from torsion associated with spin degrees of freedom. We show that these interactions lead to a novel mechanism for producing singlet fermions in the early Universe. These fermions can play the role of dark matter particles. The mechanism is operative in a large range of dark matter particle masses: from a few keV up to ∼10^{8}\u2009\u2009GeV. We discuss potential observational consequences of keV-scale dark matter produced this way, in particular for right-handed neutrinos. We conclude that a determination of the primordial dark matter momentum distribution might be able to shed light on the gravity-induced fermionic interactions.