Baryogenesis, Dark Matter and the Pentagon

TL;DR

This work ties the baryon asymmetry of the universe to the dark matter density via spontaneous baryogenesis in the Pentagon model. A PNGB with an explicitly broken accidental symmetry generates an early asymmetry that acts as a chemical potential for baryon number, which coupled with electroweak sphalerons yields the observed baryon asymmetry, while the same dynamics produce a PNGB condensate that can serve as dark matter. In the Pentagon realization, a dimension-$7$ penta-baryon-violating operator at scale $M_b$ and a symmetry-breaking scale $f$ relate the baryon asymmetry and dark matter, but achieving the correct densities without conflicting proton-decay constraints requires $M_b \sim 10^{8}$–$10^{10}$ GeV and careful UV completion; otherwise dark matter is better described by a QCD axion. Overall, the mechanism is compelling in principle but faces significant model-building hurdles within the minimal Pentagon framework.

Abstract

We present a new mechanism for baryogenesis, which links the baryon asymmetry of the universe to the dark matter density. The mechanism arises naturally in the Pentagon model of TeV scale physics. In that context, it forces a re-evaluation of some of the assumptions of the model, and we detail the changes that are required in order to fit observations.