Emergence of phantom cold dark matter from spacetime diffusion

TL;DR

This paper proposes that stochastic evolution of spacetime metrics during early cosmology can produce phantom cold dark matter, which behaves like conventional dark matter and could explain key cosmological phenomena.

Contribution

It introduces a novel mechanism where spacetime diffusion generates phantom dark matter, linking stochastic metric evolution to dark matter phenomenology without quantizing gravity.

Findings

Phantom dark matter is produced at the end of inflation.

Its average energy density is positive, consistent with dark matter.

Potential to explain structure formation and galactic dynamics.

Abstract

A way to reconcile general relativity and quantum field theory without quantising the geometry is to demand the metric evolve stochastically. In this article, we explore the consequences of such a proposal at early cosmological times. We find the stochastic evolution results in the spatial metric diffusing away from its deterministic value, generating phantom cold dark matter (CDM). It is produced primarily at the end of the inflationary phase of the Universe's evolution, with a statistical distribution that depends on the specifics of the early-times cosmological model. We find the energy density of this phantom cold dark matter is positive on average, a necessary condition to reproduce the cosmological phenomenology of CDM, although further work is required to calculate its mean density and spatial distribution. If the density is cosmologically significant, phantom dark matter acts on the geometry in a way that is indistinguishable from conventional CDM. As such, it has the potential to reproduce phenomenology such as structure formation, lensing, and galactic rotation curves. We conclude by discussing the possibility of testing hybrid theories of gravity by combining measurements of the Cosmic Microwave Background with tabletop experiments.