Possibility of Additional Intergalactic and Cosmological Dark Matter

TL;DR

This paper proposes that the universe's entropy is far below the holographic limit, suggesting the existence of additional dark matter in the form of massive primordial black holes beyond known dark matter.

Contribution

It introduces the hypothesis that dark matter includes extremely massive primordial black holes to account for the entropy gap in the universe.

Findings

Entropy of known entities is twenty orders below the holographic limit.

Primordial black holes could account for the missing entropy.

Supports the existence of additional dark matter beyond current models.

Abstract

The entropies of the known entities in the universe add to a total which is some twenty orders of magnitude below the holographic limit. Based on an assumption that the entropies should saturate the limit, we suggest that there exists dark matter, in the form of extremely massive primordial black holes, in addition to the dark matter known to exist inside galaxies and clusters of galaxies.