On the Origin and Nature of Dark Matter

TL;DR

This paper explores the thermodynamic origins of dark matter, proposing primordial black holes formed in the early universe as a primary candidate, and discusses observational strategies for detecting such objects.

Contribution

It links entropy and thermodynamics to dark matter origin, critiques existing bounds, and advocates for primordial black holes as detectable dark matter candidates.

Findings

Primordial black holes could account for dark matter.

Existing bounds on massive dark objects are challenged.

Microlensing experiments can detect primordial black holes.

Abstract

It is discussed how the ideas of entropy and the second law of thermodynamics, conceived long ago during the nineteenth century, underly why cosmological dark matter exists and originated in the first three years of the universe in the form of primordial black holes, a very large number of which have many solar masses including up to the supermassive black holes at the centres of galaxies. Certain upper bounds on dark astrophysical objects with many solar masses based on analysis of the CMB spectrum and published in the literature are criticised. For completeness we discuss WIMPs and axions which are leading particle theory candidates for the constituents of dark matter. The PIMBHs (Primordial Intermediate Mass Black Holes) with many solar masses should be readily detectable in microlensing experiments which search the Magallenic Clouds and measure light curves with durations of from one year up to several years.