Baryon-dark matter coincidence in mirrored unification

About 80% of the mass of the present Universe is made up of the unknown (dark matter), while the rest is made up of ordinary matter. It is a very intriguing question why the mass densities of dark matter and ordinary matter (mainly baryons) are close to each other. It may hint the identity of dark matter and furthermore the structure of a dark sector. A mirrored world provides a natural explanation to this puzzle. On the other hand, if the mirror-symmetry breaking scale is low, it tends to cause cosmological problems. In this work, we propose a mirrored unification framework, which breaks mirror symmetry at the grand unified scale, but still addresses the puzzle. The dark matter mass is strongly related with the dynamical scale of quantum chromodynamics, which explains the closeness of the dark matter and baryon masses. Intermediate-energy portal interactions share the generated asymmetry between the visible and dark sectors. Furthermore, our framework is safe from cosmological issues by providing low-energy portal interactions to release the superfluous entropy of the dark sector into the visible sector.