What Justifies the Slight Preponderance of Matter Over Anti-Matter?

[adrianxw]

TL;DR

Matter / antimatter

I have seen the term "slight preponderance" used many times to account for the apparent imbalance of matter and antimatter. I am not aware of the scientific justification for this however. Indeed, I have recently watched a lecture where, again, it is stated that we live in a matter universe. How is it KNOWN that, for example, the Coma cluster of galaxies is NOT made of stars fusing anti hydrogen to anti Helium? I would expect such a reaction to produce identical quantities of radiation, radiation which would be exactly the same as that produced by the reaction in the sun.

 

[mfb]

The space between galaxies is not empty. If some galaxies would be made out of antimatter then there should be a transition region with a lot of annihilation ongoing. We don't see any evidence of such a region.

This has been asked many times and you'll find many more explanations with the search function.

 

[adrianxw]

Intergalactic space may contain matter and antimatter, but it is so rarified that opportunities for anhialations are few and far between, the expansion of the universe makes such interactions progressively unlikely. It is quite possible that in the early universe, this did occur.

I did start with the search function, do so yourself, see what comes up. If you do not know the site, you search for "antimatter" or similar. I was not looking for insight in how to power a starship with the stuff.

 

[mfb]

Intergalactic space may contain matter and antimatter, but it is so rarified that opportunities for anhialations are few and far between, the expansion of the universe makes such interactions progressively unlikely. It is quite possible that in the early universe, this did occur.

People have calculated it. No, it doesn't work.

I did start with the search function, do so yourself, see what comes up.

I have replied to a few of these threads myself, I know they exist.
Here a quick search result for "antimatter galaxies" in this forum: One thread, another thread, a third one, yet another one, a related discussion, ...

 

[adrianxw]

>>> People have calculated it. No, it doesn't work.

So it MUST be right.

Interesting that they cannot calculate why that should be the case. Or bother looking for any alternatives.

 

[Ibix]

Or bother looking for any alternatives.

That's right! No scientist has ever had any interest in making a name for themself by proposing a plausible solution to one of the great unsolved problems in physics.

Don't mistake lack of success for lack of trying.

 

[Torbert]

With the observed percentage of charged matter residing at 4.7 percent and antimatter merely reverse charged regular matter, well, the 'antimatter' may have been simply not stable. The 95% of mass/energy in the observed universe that carries no detectable charge indicates factors not being addressed by the question. We no longer consider the universe to be divided exclusively into charged and reversed charged matter, quite the opposite, with only one particle in twenty carrying charge the universe seems to care very little about 'antimatter' factors.
Not that it is unimportant, merely that it is a minor rather than a major factor.
I can come up with more than one speculation on why, but with none being falsifiable at this point they are irrelevant to this forum.

 

[Ibix]

With the observed percentage of charged matter residing at 4.7 percent and antimatter merely reverse charged regular matter, well, the 'antimatter' may have been simply not stable. The 95% of mass/energy in the observed universe that carries no detectable charge indicates factors not being addressed by the question.

My reading of this is that you think only particles carrying an electric charge can have anti-particles. If so, this is incorrect.

 

[mfb]

With the observed percentage of charged matter residing at 4.7 percent and antimatter merely reverse charged regular matter, well, the 'antimatter' may have been simply not stable.

We produce antimatter in the lab routinely. It is as stable as matter.

The 95% of mass/energy in the observed universe that carries no detectable charge indicates factors not being addressed by the question.

It is a separate question. These 95% are neither matter nor antimatter, and not decay products of them either.

 

[Vanadium 50]

It is as stable as matter.

That's actually not known. The proton lifetime is > 10³⁴ years. The antiproton lifetime is known to be > ~10¹ years from direct observation and > ~10⁶ years indirectly. There are theoretical reasons that the proton and antiproton lifetime should be the same, but that is what is known experimentally.

However, that explanation doesn't work. Having antiprotons decaying at the time of recombination would make the CMBR non-thermal.

 

[mfb]

The experimental limits on antimatter are worse, of course, but good enough to rule out large-scale decays before nucleosynthesis.

BASE trapped hundreds (?) of antiprotons for over a year and didn't see any proton-antiproton annihilation. I don't know what their sensitivity for antiproton decays would be, but a significant efficiency would help with a better lower limit on the lifetime (assuming reasonable decay channels, i.e. a high energy charged lepton generated).

 

[Justin Hunt]

Well we certainly have good evidence above that the observable universe is dominated by matter, but does this really tell us anything about the entire universe? if the size of our observable universe compared to the entire universe is comparable to the size between our solar system and the milky way galaxy then our observable universe wouldn't necessarily be a good indicator. what kind of evidence do we have that the entire universe is dominated by matter rather than antimatter?

 

[Bandersnatch]

Well we certainly have good evidence above that the observable universe is dominated by matter, but does this really tell us anything about the entire universe? if the size of our observable universe compared to the entire universe is comparable to the size between our solar system and the milky way galaxy then our observable universe wouldn't necessarily be a good indicator. what kind of evidence do we have that the entire universe is dominated by matter rather than antimatter?

It's true one can't know that, observationally. But it's of no consequence* insofar as the question at hand, because having antimatter (or matter) patches in a larger universe does not solve the problem with imbalance in each of the patches taken separately.
Instead of the question: 'why did nucleosynthesis produce more of one kind of matter' you now have the question: 'why did nucleosynthesis produce more of one kind of matter in each of the causally separated patches'.
It's not like one can just solve the problem by saying the nucleosynthesis produced a homogeneous soup of particles and antiparticles and then half of those particles were left for us to be observed, while the other half was spirited away to beyond the cosmic event horizon, where they now reside and arrange themselves in systems capable of asking questions about baryon asymmetry.

*I was trying to avoid saying 'it doesn't matter'

 

[Justin Hunt]

Well, it actually does matter. but, the significance of our observable universe being dominated by matter or antimatter would depend on 1. the relative size of our observable universe to the entire universe and 2. the matter and antimatter composition of the entire universe. Now, it is a very likely scenario that the entire universe is dominated by Matter which would mean our observable universe would 100% be guaranteed to be dominated by matter as well. But, even if the whole universe were to consist of globs of matter and globs of antimatter, if these globs are many magnitudes larger than our observable universe it would be very unlikely for our observable universe to happen to fall on a boundary location rather than an area dominated by one or the other.

My point is that our observable universe is not necessarily a good indication of the entire universes matter antimatter composition based solely on observational evidence since we have no idea how large the entire universe even is. This would be like a bacteria claiming a chess board is all white or all black because the square he happens to be on is all white or all black and it is all it can see.

 

[Bandersnatch]

The point is that whether there are or aren't any antimatter islands out there doesn't help you understand why the asymmetry exists in each of those places. If you knew for a fact that such islands existed, then you'd have to explain not only why is there asymmetry, but also why does it favour one or the other kind of matter depending on location.
So no, we don't know that. But if we did it wouldn't help solve the problem.

 

[Justin Hunt]

Well, wouldn't the obvious answer be that matter and antimatter annihilate each other? I see there only being two possibilities. 1. there is some kind of imbalance that has caused the entire universe to be dominated by matter versus antimatter. or 2. there is an imbalance in the distribution of matter and antimatter in the universe that has lead areas to be dominated by one or the other.

currently our models go with scenario 1 and we have found some disparities between the two, but not enough for a full explanation yet.

 

[PeterDonis]

wouldn't the obvious answer be that matter and antimatter annihilate each other?

We already know that happened in the early universe, because there are about a billion photons per baryon in our current universe; those photons are left over from matter-antimatter annihilation in the early universe.

 

[BlackWhole]

Isn't it possible that the missing anti-matter has slipped past the edge of the observable universe? And if the entire universe is as large as some calculations make it out to be, then couldn't the imbalance in matter-antimatter density in our observable universe be a random statistical occurrence, with essentially uniform distribution throughout the entire universe? Or would we be able to deduce this from observations of the early universe?

 

[mfb]

There is no plausible mechanism that could produce a matter/antimatter asymmetry with the observed magnitude and large enough to cover the whole observable universe.

For random chance you would expect smaller asymmetries to be much more common, and we would expect to be in a spot with just the minimal asymmetry needed to support some life. We can't rule out a really freak coincidence but that is not a good option. If you see a die roll "6" a trillion times in a row you don't expect it to be unbiased - you expect that some mechanism makes it much more likely to roll 6.

 

[metastable]

There is no plausible mechanism that could produce a matter/antimatter asymmetry with the observed magnitude and large enough to cover the whole observable universe.

No one explicitly answered A or B when I asked about this in a different thread:

a) it is known that relativistic jets are unable to concentrate matter or antimatter in different regions

or

b) it could be possible, but since no proof of such a mechanism has previously been published, there is no “known” way

https://www.physicsforums.com/threads/antimatter-in-relativistic-jets.972631/

 

[mfb]

No one explicitly answered A or B when I asked about this in a different thread:

It is impossible to completely rule out things about the universe.
Not that it would matter for the topic here.

 

[metastable]

Not that it would matter for the topic here.

I can’t tell if that’s a very subtle pun, but puns aside, wouldn’t the relevance of the question depend on whether physicists determine whether or not there are black holes outside the observable universe and/or whether there’s an upper size limit on black holes outside the observable universe?

 

[mfb]

It was not a pun.
There are almost certainly black holes outside the observable universe. They are within it, why should something outside make their formation impossible? A size limit is just coming from the overall size of the observable universe at a given point.
But they have nothing to do with the matter/antimatter asymmetry in the early universe. You can't randomly put two things together and expect that to make sense.

 

[PeterDonis]

No one explicitly answered A or B when I asked about this in a different thread

No, no one cared to continue repeating an answer that you ignored.

 

[Torbert]

We already know that happened in the early universe, because there are about a billion photons per baryon in our current universe; those photons are left over from matter-antimatter annihilation in the early universe.

If charged matter dominated the expanding universe and mostly self annihilated, leaving only one part in twenty as charged matter, then the photon count could be related, or it may not be.
This 'imbalance' is derived from the assumption of a virtual particle similar to those we apparently are detecting today, two pieces of regular matter with opposite charges, same as appeared in the first 10^-43 seconds.
How correct is this assumption?
Are we not detecting the Dark Matter and Dark Energy components in today's virtual particles for the same reasons we do not detect them in space, lack of technology at this time? Are the virtual particles primarily comprised of rapidly dissipating dark 'stuff', bypassing our detectors? Accelerating our expansion?
No speculation, just questions, parts of which are silly.

 

[mfb]

If charged matter dominated the expanding universe and mostly self annihilated, leaving only one part in twenty as charged matter

Check what you quoted, the fraction was about 1 part in a billion.

This 'imbalance' is derived from the assumption of a virtual particle similar to those we apparently are detecting today, two pieces of regular matter with opposite charges, same as appeared in the first 10^-43 seconds.
How correct is this assumption?
Are we not detecting the Dark Matter and Dark Energy components in today's virtual particles for the same reasons we do not detect them in space, lack of technology at this time? Are the virtual particles primarily comprised of rapidly dissipating dark 'stuff', bypassing our detectors? Accelerating our expansion?

None of that makes any sense.
Virtual particles are mathematical tools in perturbation theory, a way to calculate the probability of some processes. They are not physical objects, and therefore nothing you could detect. It would be like trying to detect the concept of the number 3 in the universe.