Computation of gravitational particle production using adiabatic invariants

Abstract

Analytic and numerical techniques are presented for computing gravitational production of scalar particles in the limit that the inflaton mass is much larger than the Hubble expansion rate at the end of inflation. These techniques rely upon adiabatic invariants and time modeling of a typical inflaton field which has slow and fast time variation components. A faster computation time for numerical integration is achieved via subtraction of slowly varying components that are ultimately exponentially suppressed. The fast oscillatory remnant results in production of scalar particles with a mass larger than the inflationary Hubble expansion rate through a mechanism analogous to perturbative particle scattering. An improved effective Boltzmann collision equation description of this particle production mechanism is developed. This model allows computation of the spectrum using only adiabatic invariants, avoiding the need to explicitly solve the inflaton equations of motion.

Quantum interference in gravitational particle production

“…A related feature is that the leading phase Φ (n→2) k,leading diverges in the limit that m χ /m φ → 0. Let's now compare the squared amplitudes between the current computation and an earlier work by some of the present authors [64]. From the latter, we have the estimate…”

“…In this paper we explain these oscillatory features as the result of a quantum effect arising from an interference of different amplitudes, which are analogous to gravitationallymediated nonthermal scattering processes, 1 nφ → 2χ for n ≥ 1. Typically the 2φ process dominates nonthermal scattering production, but it has recently been pointed out [64] that the nφ processes with n = 2 may also be important. Most of the effect comes from interference of 2φ with the next leading amplitude, which is 3φ if cubic interactions exist and 4φ otherwise.…”

Scalar field couplings to quadratic curvature and decay into gravitons

“…σ αβγ ] = 0. (B 22). In the same way, we can show that[σ αβγδ ] = S αβγδ ≡ 1 3 R αγβδ + R αδβγ , (B.23) [σ αβγδµ ] = 3 4 ∇ µ S αβγδ + ∇ δ S αβγµ + ∇ γ S αβδµ , (B.24) [ 3 σ] = 4 15 R µν R µν − R µνρσ R µνρσ +…”

Snowmass2021 Cosmic Frontier White Paper: Ultraheavy particle dark matter

“…Typically, although though there are important exceptions, production is most efficient when the DM mass is comparable to the inflationary Hubble scale, m χ ∼ H inf , and since cosmological observations constrain H inf 10 14 GeV, such models usually involve superheavy elementary particles. Notable recent work has explored models of higher-spin DM [54][55][56][57][58][59], models of superheavy DM with m χ > H inf [60][61][62], improved analytical techniques [63][64][65], and cosmological signatures such as isocurvature [66][67][68].…”