Off-shell Dark Matter: A Cosmological relic of Quantum Gravity

TL;DR

This paper proposes a novel quantum gravity-inspired model where off-shell modes of quantum fields, arising from spacetime nonlocality, serve as cold dark matter, with specific implications for early universe cosmology and observable signatures.

Contribution

It introduces off-shell dark matter originating from quantum gravity effects, linking its production to the early universe and providing testable predictions for cosmology.

Findings

Off-shell dark matter is produced only in the early universe and then decouples gravitationally.

The model relates reheating temperature to inflaton mass, constraining inflationary parameters.

Predicted observable signatures include effects on small-scale matter power spectrum.

Abstract

We study a novel proposal for the origin of cosmological cold dark matter (CDM) which is rooted in the quantum nature of spacetime. In this model, off-shell modes of quantum fields can exist in asymptotic states as a result of spacetime nonlocality (expected in generic theories of quantum gravity), and play the role of CDM, which we dub off-shell dark matter (OfDM). However, their rate of production is suppressed by the scale of non-locality (e.g. Planck length). As a result, we show that OfDM is only produced in the first moments of big bang, and then effectively decouples (except through its gravitational interactions). We examine the observational predictions of this model: In the context of cosmic inflation, we show that this proposal relates the reheating temperature to the inflaton mass, which narrows down the uncertainty in the number of e-foldings of specific inflationary scenarios. We also demonstrate that OfDM is indeed cold, and discuss potentially observable signatures on small scale matter power spectrum.