Computation of Gravitational Particle Production Using Adiabatic Invariants

TL;DR

This paper introduces analytic and numerical methods based on adiabatic invariants to efficiently compute gravitational scalar particle production after inflation, especially for large inflaton masses, improving computational speed and modeling accuracy.

Contribution

It develops a novel approach using adiabatic invariants and time modeling to simplify and accelerate the calculation of gravitational particle production in inflationary cosmology.

Findings

Efficient numerical computation achieved via subtraction of slowly varying components.

Particle production spectrum computed without solving inflaton equations explicitly.

Mechanism analogous to perturbative scattering for large inflaton masses.

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.