Gravitational production of super-Hubble-mass particles: an analytic approach

Abstract

Through a mechanism similar to perturbative particle scattering, particles of mass m χ larger than the Hubble expansion rate H inf during inflation can be gravitationally produced at the end of inflation without the exponential suppression powers of exp(−m χ /H inf ).Here we develop an analytic formalism for computing particle production for such massive particles. We apply our formalism to specific models that have been previously been studied only numerically, and we find that our analytical approximations reproduce those numerical estimates well.

Gravitational vector Dark Matter

“…We focus on a massive scalar hadron bound state, as massive higher-spin bound states only exist in the low-energy regime where the peculiar behaviour of massive fundamental higher-spin states (e.g. longitudinal modes of spin 1, see [32][33][34][35]) does not take place. Then the bound-state field equations in the homogenous limit areẌ…”

Gravitational production of superheavy dark matter and associated cosmological signatures

“…However, as noted recently in [30], during an inflaton oscillation regime [31,32], where the scale factor oscillates very rapidly, dark matter particles with number density proportional to H 3 can be produced. An analytical approach for this case is developed recently in [33].…”

Note on the reheating temperature in Starobinsky-type potentials

“…We note that if we invert this function the obtained result coincides to a great extent with the relation in equation (32) of [29], reached through a next-to-leading order expansion. Now, by equating (17) and (19) we get a relation between the reheating temperature and the spectral index of scalar perturbations, which is represented in Fig. 3.…”

“…Working in the Einstein frame, R 2 -gravity leads to the well-known Starobinsky potential [2], which has been recently studied as an inflationary potential, and the reheating temperature provided by the model is related to its corresponding spectral index [12][13][14] (see also [15] for the calculation of the reheating temperature when inflation come from a constant-roll era). However, contrary to [16,17] where the authors consider the gravitational production of superheavy particles, in those papers the reheating mechanism is not taken into account; instead of it, it is assumed that during the oscillations of the inflaton field the effective Equation of State (EoS) parameter is constant. From our viewpoint, it is difficult to understand how it is possible to make any meaningful statements about reheating temperature without consideration of its concrete mechanisms, apart from the hypothesis of instant thermalization [18], which has to be still justified [19].…”