Cosmology of the Twin Higgs without explicit $\mathbb{Z}_2$ breaking

Understand

The cosmology of the Twin Higgs requires the breaking of the $\mathbb{Z}_2$ symmetry, but it is still an open question whether this breaking needs to be explicit.

• In this paper, we study how the Mirror Twin Higgs could be modified to be compatible with current cosmological constraints without explicit $\mathbb{Z}_2$ breaking.
• We first present a simple toy model that can realize baryogenesis without explicit $\mathbb{Z}_2$ breaking or reaching temperatures that would lead to domain walls.
• The model can also either solve the $N_{\text{eff}}$ problem and bring the abundance of mirror atoms to an allowed level or provide the correct dark matter abundance.