Non-minimally coupled Scalar Dark Matter from Inflationary Fluctuations

TL;DR

This paper explores how non-minimal gravitational coupling of light scalar fields during inflation suppresses large-scale fluctuations, enabling these fields to account for dark matter without conflicting with observational constraints.

Contribution

It introduces a novel mechanism where non-minimal coupling suppresses large-scale fluctuations, allowing scalar fields to be viable dark matter candidates.

Findings

Large-scale fluctuations are suppressed due to non-minimal coupling.

Scalar fields can account for all dark matter without large isocurvature signals.

The mechanism aligns with cosmological observations and dark matter abundance.

Abstract

It is well known that light scalar fields present during inflation are coherently excited. We show that if the field couples to gravity in a non-minimal way, the fluctuations at large scales are suppressed with respect to the small scales ones. This fact allows for the field excitations to make a sizeable contribution to the energy density of the universe without generating too large isocurvature fluctuations at observable scales. We show that this mechanism could generate all the observed dark matter and study the main cosmological implications of this setup.