Speaker
Description
The discovery of a nano-Hz stochastic gravitational wave background by Pulsar Timing Array (PTA) collaborations can be interpreted as arising from a strongly supercooled phase transition in a nearly conformal dark sector. I will present a concrete model for this phase transition, and show that the strong supercooling it requires generically dilutes any pre-existing baryon asymmetry and dark matter abundance. I will then discuss how this apparent problem can be turned into a solution by exploiting the built-in out-of-equilibrium dynamics of the transition to generate both after the phase transition. I will present a neutron portal framework connecting the resulting dark baryon asymmetry to the visible sector, discuss its ultraviolet completion, and show how it naturally explains the baryon-dark matter coincidence problem. I will conclude with a discussion of baryon inhomogeneity effects and other phenomenological consequences of this framework.