My idea on what happened to all the antimatter.

[Haelfix]

To the OP. In order to have a matter/antimatter asymmetry the necessary and sufficient conditions were layed out by Sakharov in the 60s.

A black hole in and of itself is not sufficient to meet these bounds, however a black hole and other physics is. So while this isn't exactly what you had in mind, its somewhat related.

For instance Grand unified theories provide a mechanism to have baryon number nonconservation and CP violation. So indeed, if you combine a black hole with something like that, you presumably satisfy the conditions necessary.

This is what's called black hole baryogenesis, and it has been looked at before (Hawkings and Zeldovitch were the pioneers afair). The idea being, a black hole while its radiating under the Hawking process can spit out a bunch of heavy particles, and they in turn can violate lepton or baryon number. The black hole in that case, acts like a sort of multiplier to the final observed asymmetry.

The problem is, you need a lot of primordial black holes in the early universe to be of relevance, and this in turn is very sensitive to inflation and is highly model dependant. Moreover Sphaleoron processes damp some of this as well.

You'd probably have to search arxiv for the modern parameter spaces where this hypothesis lives in. I don't know off the top of my head if its been falsified or whether its still active.

 

[TalonD]

where is all the antimatter. I was reading up on Fienman diagrams, in an electron / antielectron(positron) interaction, the two particles anihilate and yeild a high energy photon. but that is mathmatically equivilant to an electron absorbing a high energy photon and traveling backwards in time as a positron. So from that argument, an antiparticle is the same as a particle that is traveling back in time. So could the absence of antimatter be a consequence of the one directional nature of time? So to have equal quantities of matter and antimater, time would have to be bidirectional? Seems as reasonable as primordial black holes?

 

[derek.basler]

yea that actually sounds pretty interesting. But we can create anti-particles, so that would break times one-directionality right?

 

[Vanadium 50]

There are multiple parts to this question. The first question is "is there a global baryon asymmetry (the technical term for the matter-antimatter asymmetry) or are there pockets of matter and pockets of antimatter?" We don't really know the answer to this, but we do know that if there are pockets, they are quite large - perhaps 100 Mpc across. We know this because we don't see evidence of nearby annihilation radiation.

The second question is whether there were enough primordial black holes to force an asymmetry. I don't know for sure, but I suspect that the answer is "no". If the expected asymmetry was due to chance alone, it would mean you'd end up with an excess that is about the size of the square root of the number of PBH's. For example, a 10% matter-antimatter asymmetry would mean ~100 PBH's. A 1% asymmetry would mean ~10,000 PBH's.

The problem is that there's not enough dark matter out there. There is ~8x as much dark matter (including PBH's) as ordinary matter, which would suggest only 64 PBHs. We know that dark matter is very smoothly distributed, and we would need many trillions of them, not just 64. So this doesn't work out well quantitatively.

 

[butthead]

isnt it possible that the antimatter might have got liberated to form something outside the uiniverse and may be it is supporting the universe