The predominance of matter over antimatter I thought was explained by symmetry breaking at the ultra extreme conditions of early universe? Would there be a twin universe for other broken symmetries?
That's what is explained in the Janus model, both universes coexist in the same space and are rejecting each other through gravity, matter "won" over antimatter only by a tiny bit but sufficient to allow large portions of matter to remain. Though the appearance of both at the early times of the universe was in beyond colossal amounts, both being annihilated by each other when they met.