Where is all the Antimatter?

Question

This is obviously a duplicate of If matter and antimatter... However, it's now four to five years after a swarm of videos were made on this subject. At the time, there was a consensus that the LHC would soon be able to tell us if there's some asymmetry that might explain why matter and antimatter didn't completely annihilate each other in the first few seconds of BBN.

So what is the current state of this issue? Is there any theory that can explain how a photon could split into unequal parts of matter and antimatter? How big a problem is this?

If you want an update on some old post, the correct thing to do is to offer a bounty ("Current answers are outdated") instead of reposting it. — AccidentalFourierTransform, Nov 27 '18 at 01:13
@Joao - I've got that, but I'm wondering if the problem has grown with time. For example, we still haven't found Dark Matter, but the crisis has grown since 2015 because LUX and LHC have ruled out the more obvious SUSY models. — , Nov 27 '18 at 01:16
As far as I've read during my time at the university, there's currently no concrete explanation on the assymetry of matter and antimatter. In fact, it rests as one of the top problems to be solved in theoretical physics, so it is an exciting area of research if you're interested. — Charlie, Nov 27 '18 at 01:34
@Charlie - Thank you. I don't how old your reading materials were at the university, but I was hoping for a 2018 update on LHC experiments. I saw a fluff science news piece that recent LHC experiments had all but confirmed there was no asymmetry in anti-Hydrogen, and was hoping to find some reference-able articles. — , Nov 27 '18 at 01:52
@safesphere That is not correct: searches for CP violation which would explain the matter-antimatter asymmetry are an active field of research with several fronts, not just at LHC. If you have other information, please expand your comment into a proper answer. — rob, Nov 27 '18 at 05:39
@safesphere The question is why was the initial production asymmetrical. If your answer is "I don't care" that's fine, but it's a legitimate scientific query. — Señor O, Nov 27 '18 at 06:55
@SeñorO I've said there is no problem not because I dodn't care, but because the problem is a result of a wrong assumption that the initial production happens after the Big Bang. If you admit that the production happens at the moment of the Big Bang, then the problem disappears, because the asymmetry of matter at the initial moment directly follows from the asymmetry of time that starts at this moment going in only one direction. — safesphere, Nov 27 '18 at 17:50
@safesphere - what "asymmetry of matter" are you talking about? In the first few moments of creation, there was only radiation. After the universe cooled, photons began splitting into matter and antimatter and then back again. Every photon produced an equal amount of matter and antimatter. What chemical process exists that created more matter than antimatter from radiation? — , Dec 02 '18 at 15:52
@DonaldAirey "In the first few moments of creation, there was only radiation." - According to what? This is just a speculation. Get rid of this wrong idea and the problem disappears. — safesphere, Dec 02 '18 at 16:28
@safesphere - You can't have baryons until you have hadrons. Quarks didn't cool enough to form hadrons until about a microsecond after the start of time. Antimatter and matter were in perfect equilibrium as I understand it. Please explain the physics that allowed for more matter than antimatter to be left at the end of the Hadron Epoch. — , Dec 02 '18 at 17:30

score 2 · Answer 1 · answered Nov 27 '18 at 07:19

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Here is a solution which would be matching quantitatively (in contrast to all current solutions):

A split big bang with two opposite time directions. Creation of matter and antimatter at the moment $t0$, but also at the moment $-t0$. Matter and antimatter are separated by the propagation of matter and antimatter in two opposite time directions.

This proposal is no ready-made theory, and it would leave many open questions, but it shows that quantitative solutions are possible and that perhaps not all resources have been explored yet in physics.

answered Nov 27 '18 at 07:19

Moonraker

3,135

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Do you have a link to a paper for this idea ? Is it a personal theory ? – StephenG - Help Ukraine Nov 27 '18 at 07:56
This appears to be related to the idea that antimatter is matter traveling backwards in time. – Nat Nov 27 '18 at 08:24
@StephenG This is an old idea. I remember reading it decades ago. I've been looking for a decent ref, but it's hard to find among all the scifi & woo. The best I've found so far is from Universe Today – PM 2Ring Nov 27 '18 at 08:28
@PM2Ring I also went web searching for it and all I found was references to a certain TV show. Irritating when that kind of thing happens. – StephenG - Help Ukraine Nov 27 '18 at 08:34
@Nat, StephenG: This is no theory put the simple consideration of a geometrical fact, which unfortunately is not sufficiently considered in the research of baryogenesis. However, the main problem of the solution is that experimentally, antimatter is not observed as moving in the opposite direction of our time arrow. That means that the solution is not as simple as that. – Moonraker Nov 27 '18 at 08:48
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@StephenG I found this arXiv article Dark Matter, Antimatter, and Time-Symmetry by Trevor Pitts. I'll keep looking... – PM 2Ring Nov 27 '18 at 08:51
@StephenG This looks interesting, and it mentions work by Sean Carroll, Alan Guth, and Julian Barbour. – PM 2Ring Nov 27 '18 at 09:26
@Moonraker I'm quite fond of this theory. However, it's somewhat unsatisfying because it appears to be impossible to test. – PM 2Ring Nov 27 '18 at 09:34
@safesphere,(1) "Matter/ antimatter creation event" means mainly the stage of baryogenesis after the big bang, supposing that baryogenesis does not happen exactly at the same moment as the big bang. (as described in the abstract of the article of Trevor Pitts, cited by PM 2Ring). – Moonraker Nov 27 '18 at 13:33
@safesphere (2) For fundamental questions of physics about time you must refer primarily to proper time of the particles and only secondarily to the coordinate time flow of some observer. The proper time of (anti) particles is always positive. However, an observer would always observe one of the directions as positive (in his own direction) and one as negative (in the opposite direction). – Moonraker Nov 27 '18 at 13:34
@Moonraker - Where do you get the idea that antimatter is not moving backwards in time? As I understand CPT symmetry, an anti-atom moving forward in time would break CPT symmetry, and all the reports I've read seem to confirm that nothing they've found yet breaks this symmetry (which, I would assume, strongly indicates that anti-atoms are moving backwards in time, as suggested). – Nov 27 '18 at 16:48
@Donald Airey, see this experiment. Your CPT question would be worth a new question because it seems to be quite complex. – Moonraker Nov 27 '18 at 17:09
@Moonraker (1) I see your point. It is different from mine, so I have deleted my comment, as it was not as applicable to your answer as I initially thought. Good answer anyway +1. – safesphere Nov 27 '18 at 17:23
@Moonraker (2) I don't quite follow. Are you saying that in the rest frame, the proper time of an antiparticle is the opposite of the proper time of the observer? If so, can you please provide a reference or elaborate? Thanks! – safesphere Nov 27 '18 at 18:36
@DonaldAirey "an anti-atom moving forward in time would break CPT symmetry" - Not at all. The CPT symmetry says that we see an atom moving back in time as an anti-atom moving forward in time. So all anti-matter moves forward in time and obeys the laws of causality. It just has all quantum numbers and parity reversed. – safesphere Nov 27 '18 at 18:45
@safesphere - "we see an atom moving back in time as an anti-atom moving forward in time" What? At CERN, they have a magnetic bottle filled with anti-Hydrogen. Is this particle moving forward or backward in time? – Dec 02 '18 at 15:58
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@DonaldAirey Anti-hidrogen moves forward in time and obeys the causality laws. According to John Wheeler, this can also be seen as hydrogen moving back in time (although the causality is not reversed): https://en.wikipedia.org/wiki/Wheeler-Feynman_absorber_theory – safesphere Dec 02 '18 at 16:11

Where is all the Antimatter?

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