Mirror Dark Matter and Core Density of Galaxies

TL;DR

The paper investigates whether an asymmetric mirror universe, with mirror baryons as dark matter, can simultaneously address the core-density problem in galactic halos, the cosmic relic density, and microlensing observations. It argues that mirror H'-H' interactions yield self-interacting dark matter, while the core remains optically thick to mirror photons, avoiding dissipation-driven collapse. By tying the mass-scaling parameter $\zeta$ to both neutrino phenomenology and microlensing, the model yields a consistent relic density and predicts galaxy-scale structure set by mirror Silk damping, potentially fragmenting into ~$0.5\,M_\odot$ objects. If viable, this framework provides a unified explanation for $\Omega_{DM}$, MACHO masses, and halo core properties beyond the standard model.

Abstract

We present a particle physics realization of a recent suggestion by Spergel and Steinhardt that collisional but dissipationless dark matter may resolve the core density problem in dark matter-dominated galaxies such as the dwarf galaxies. The realization is the asymmetric mirror universe model introduced to explain the neutrino puzzles and the microlensing anomaly. The mirror baryons are the dark matter particles with the desired properties. The time scales are right for resolution of the core density problem and formation of mirror stars (MACHOs observed in microlensing experiments). The mass of the region homogenized by Silk damping is between a dwarf and a large galaxy.