Gravitational production of a conformal dark sector

Abstract

Dark sectors with purely gravitational couplings to the Standard Model are unavoidably populated from the SM plasma by graviton exchange, and naturally provide dark matter candidates. We examine the production in the relativistic regime where the dark sector is approximately scale invariant, providing general analytical formulas that depend solely on the central charge of the dark sector. We then assess the relevance of interactions that can lead to a variety of phenomena including thermalisation, non-perturbative mass gaps, out-of-equilibrium phase transitions and cannibalism in the dark sector. As an illustrative example we consider the dark glueball scenario in this light and show it to be a viable dark matter candidate due to the suppression of gravitational production. We go on to extend these results to strongly coupled CFTs and their holographic duals at large-N with the dark dilaton as the dark matter candidate.

Dark Matter as dark dwarfs and other macroscopic objects: multiverse relics?

“…They tend to be long-lived in models with no light dark quarks. If stable enough, dark glue-balls can be acceptable DM candidates provided that the dark sector temperature is initially much smaller than the SM temperature, for example because the dark sector is populated via gravitational freeze-in [27,28]. In such a case, after confinement dark glue-balls undergo 'cannibalistic'…”

“…Furthermore, non-renormalizable operators that induce decays of dark quarks must be suppressed enough. This automatically happens at larger N [27,28,42], that also makes baryon formation more difficult.…”

Hidden dark matter from Starobinsky inflation

“…The gravitational particle production during the reheating phase 4 has been discussed in refs. [47,[59][60][61][62][63][64]. It is shown that the gravitational particle production picture in the Jordan frame gives the same result as the inflaton decay picture in the Einstein frame [60,65].…”

Computation of gravitational particle production using adiabatic invariants

“…Also, unlike the scenarios of refs. [27,[41][42][43], the phase space structure of the initial inflaton degrees of freedom is fixed by the Bunch-Davies/adiabatic vacuum prescription during inflation. It is in this sense that the particle production considered in ref.…”

“…1 In addition, see refs. [4,6,[16][17][18][19][20][21][22][23][24][25][26][27][28] for examples of superheavy dark matter motivated by UV model constructions. 2 Here super-Hubble-mass refers to a mass that is larger than the Hubble expansion rate during the quasi-dS era.…”