The effects of non Bunch-Davies initial conditions on gravitationally produced relics

TL;DR

This paper explores how non Bunch-Davies initial conditions influence the production and abundance of relic particles during inflation, revealing significant effects for certain particle types and initial states.

Contribution

It provides a general framework to analyze the impact of various initial conditions on relic production, extending beyond the standard vacuum assumption.

Findings

Non Bunch-Davies conditions can significantly alter relic abundance for some particles.

Particles with conformal symmetry breaking only from mass are less affected by initial conditions.

A wide range of dark matter masses can be achieved with different initial states and inflation scenarios.

Abstract

Typical gravitational production of relics from amplification of inflationary perturbations assumes Bunch-Davies initial conditions, i.e. a vacuum with initially no particles. In this paper we investigate the impact of non Bunch-Davies initial conditions to the final abundance of relics, with particular attention to the parameter space where the total dark matter abundance is reproduced. We present a general framework for any initial condition, through which we show their non-trivial effect on both spectrum and late-time abundance. We argue that for particles whose source of conformal symmetry breaking comes only from a mass term (spin-1/2 fermions and conformally coupled scalars), the choice of initial conditions has little impact on the mass range relevant to dark matter. For other particles, e.g. the longitudinal mode of spin-1, we see a large deviation from the standard computation. We exemplify and quantify our results with an initial thermal state and a two-stage inflation scenario, highlighting that the total dark matter can be obtained for a wide range of masses.