Mirror Matter as Self Interacting Dark Matter

TL;DR

The paper addresses the cuspy halo problem by proposing mirror matter, especially mirror hydrogen, as a self-interacting dark matter candidate. It demonstrates that the relevant transport cross section at galactic velocities, $\sigma_{tr} \sim 10^{-22}$ cm$^2$, arises from forward-peaked H'-H' scattering when many partial waves contribute, placing it in the range needed to flatten cores. Cosmological constraints in the mirror sector, including $T'/T \approx 0.5$ and $\Omega_{B'} \approx 4\Omega_B$, yield a plausible dark-matter fraction of about 20% and a substantial dark-energy component, aligning with observations. Additionally, heavier mirror masses suppress cooling via bremsstrahlung, extending halo relaxation times beyond the age of the universe and avoiding a disk-like morphology, supporting mirror hydrogen as a viable SIDM candidate with practical astrophysical implications.

Abstract

It has been argued that the observed core density profile of galaxies is inconsistent with having a dark matter particle that is collisionless and alternative dark matter candidates which are self interacting may explain observations better. One new class of self interacting dark matter that has been proposed in the context mirror universe models of particle physics is the mirror hydrogen atom whose stability is guaranteed by the conservation of mirror baryon number. We show that the effective transport cross section for mirror hydrogen atoms, has the right order of magnitude for solving the ``cuspy'' halo problem. Furthermore, the suppression of dissipation effects for mirror atoms due to higher mirror mass scale prevents the mirror halo matter from collapsing into a disk strengthening the argument for mirror matter as galactic dark matter.