I've long been an advocate of an approach to explaining the matter-antimatter asymmetry of the universe in which antimatter predominantly in a partner universe whose boundary with our own is at a shared Big Bang. A brief new paper explores the idea more formally, although the use of multiverse terminology is somewhat unfortunate for a proposal that lacks many of the flaws more commonly found in multiverse arguments.

In the multiverse, the universes can be created in entangled pairs with spacetimes that are both expanding in terms of the time variables experienced by internal observers in their particle physics experiments. The time variables of the two universes are related by an antipodal-like symmetry that might explain why there is no antimatter in our universe: at the origin, antimatter is created, by definition and for any observer, in the observer's partner universe. The Euclidean region of the spacetime that separates the two universes acts as a quantum barrier that prevents matter-antimatter from collapse.

Salvador J. Robles-Perez, "Restoration of matter-antimatter symmetry in the multiverse" (June 20, 2017).

An earlier version of the proposal from 2013 can be found here.

An earlier version of the proposal from 2013 can be found here.