I have been thinking about what happened to the anti-matter component of the universe and why it cannot have been destroyed at the formation point of the universe. We understand from the current models that a significant mass component of the universe is unaccounted for, and may be down to the missing anti-matter. We know this missing mass exists as it has an observable influence of universal masses.
My thoughts on this:-
At the start point of the universe there was an equal amount of matter and anti-matter created in the big bang.
If we accept that anti-matter and matter are true opposites [attracting each other equally] it is reasonable to expect that the anti-matter traveled out from the big bang as an expanding wave in front of the matter component, and as the anti-matter stays in front of the expanding matter they are stable to each other and do not interact except gravitationally.
It is possible that the expanding wave of anti-matter is pulling the matter universe outwards from the origin point.
Hence we can exist in an expanding universe where anti-matter and matter co-exist but only interact gravitationally on each other.