Matter-Dark Matter Coincidence and Mirror World

TL;DR

This paper proposes a new mirror world model to explain why matter and dark matter densities are similar, using the Affleck-Dine mechanism to generate asymmetric dark matter, with specific predictions for dark matter candidates and dark radiation.

Contribution

It introduces a simple mirror world scenario with asymmetric dark matter generation, predicting mirror electron or baryon dark matter and a lower bound on dark radiation.

Findings

Mirror electron as dark matter in certain parameter ranges

Mirror baryons as dark matter in other parameter ranges

Lower bound on dark radiation, ΔN_eff ≥ 0.007

Abstract

Why matter and dark matter contents of the universe are of the same order of magnitude, is one of the puzzles of modern cosmology. At the face of it, this would seem to point towards a basic similarity between matter and dark matter, suggesting perhaps the widely discussed mirror world picture as an ideal setting for a discussion of this issue. Here we outline a new and simple mirror world scenario to explain this puzzle. Our model uses Affleck-Dine mechanism to generate baryon asymmetry and dark matter relic density leading to an asymmetric dark matter picture. We find that for a certain parameter range of the model, the mirror electron is the unique possibility for dark matter whereas in the complementary parameter range, the mirror baryons constitute the dark matter. In either case, the mirror photon must have mass in the MeV range for consistency with observations. For the case of mirror electron dark matter, the model predicts a lower bound on the amount of dark radiation i.e. $\Delta N_{eff} \geq 0.007$.