A novel way to determine the scale of inflation

TL;DR

This paper demonstrates that in the FIMP dark matter model, the inflationary energy scale can be determined from dark matter properties without relying on tensor-to-scalar ratio measurements.

Contribution

It introduces a method to estimate the inflationary scale using dark matter isocurvature perturbations, mass, and self-coupling, independent of tensor modes.

Findings

Derived a narrow range for the inflationary scale $H_*$.

Showed $H_*$ can be estimated without tensor perturbation data.

Accounted for various astrophysical and cosmological constraints.

Abstract

We show that in the Feebly Interacting Massive Particle (FIMP) model of Dark Matter (DM), one may express the inflationary energy scale $H_*$ as a function of three otherwise unrelated quantities, the DM isocurvature perturbation amplitude, its mass and its self-coupling constant, independently of the tensor-to-scalar ratio. The FIMP model assumes that there exists a real scalar particle that alone constitutes the DM content of the Universe and couples to the Standard Model via a Higgs portal. We consider carefully the various astrophysical, cosmological and model constraints, accounting also for variations in inflationary dynamics and the reheating history, to derive a robust estimate for $H_*$ that is confined to a relatively narrow range. We point out that, within the context of the FIMP DM model, one may thus determine $H_*$ reliably even in the absence of observable tensor perturbations.