Gravitational production of superheavy dark matter and associated cosmological signatures

Abstract

We study the gravitational production of super-Hubble-mass dark matter in the very early universe. We first review the simplest scenario where dark matter is produced mainly during slow roll inflation. Then we move on to consider the cases where dark matter is produced during the transition period between inflation and the subsequent cosmological evolution. The limits of smooth and sudden transitions are studied, respectively. The relic abundances and the cosmological collider signals are calculated.

Cosmological collider physics and the curvaton

“…This is the focus of the "cosmological collider physics" program [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. For various recent ideas in this direction see, [18][19][20][21][22][23][24][25][26][27][28].…”

Cosmological signatures of superheavy dark matter

“…Additionally, the subscript (2) denotes the number of interaction vertices. This type of integral in the squeezed limit k 1 k 2 k 3 is well-known [17,50,53,60,103] and the details are collected in appendix. A. Eq.…”

“…From the frequency of the oscillation on the squeezed limit non-Gaussianity, one can directly obtain information about the mass of extra fields during inflation. We investigated the search for the dark matter mass in the context of cosmological collider physics in [53], targeting at the class known as superheavy dark matter (SHDM) [69][70][71][72][73][74] with mass m σ ≥ H. 1 Since the dark matter is produced gravitationally, the signal is subject to a suppression of power (H/M pl ), which makes it hardly observable in the near future experiments.…”

“…As discussed before, without further interactions σ is then a massive stable particle and interacting with other fields via the small coupling and χ as the mediator, making itself a good DM candidate. For its gravitational production during inflation, we will mostly follow the calculations in [53]. Note that we are interested in the case where the mediator field χ is a light field, i.e., m 2…”

“…which is constant in time. Assuming matter domination before reheating and radiation domination afterwards, the current DM abundance can be expressed numerically [53,73]:…”