It's possible there is no assymetry at all- maybe there are equal numbers of universes and antiverses, with opposite arrows of time (one expanding while the other contracts and vice versa) and made of dimensions that are complementary to the other.
That is what I am suspecting... However I don't think you need more than just a negative direction in time. For me, treating the entire universe like a Feynman diagram would say that an antimatter universe should propagate in a negative time direction. But that does create a question, would this antiverse be apart or part of our universe? Being that does it represent a violation in energy conservation or its solution, or does it represent a non-closed energy system. It would make sense... I don't know though.
My "
Theory" (Not really a theory, just an educated guess):
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Matter is a function in time. The direction in time is causality. There are two sub-types of causality: direction and orientation. Direction is like the flow of entropy, Orientation is like the charge of a particle. Antimatter in our universe, now, experiences entropy forwards because its direction is forwards, but it "faces" backwards. Like as if you were walking backwards. But antimatter in an antiverse has a negative time direction and orientation, it would look like matter there. But as a Feynman diagram shows, the orientation and direction are the same thing, just interpreted differently based on perspective. There is only 1 causality but it looks like 2. This is as much I can "guess" into, and I am not saying thats how it is, just what I think it looks like.
To reality, through nothing, from un-everything.