Antiparticles and Cosmology

  • #1
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There is an assumption in cosmology say that there is another universe Composed of antiparticles?
I mean that the atom composed of positron rather than an electron, anti-proton rather than a proton and anti-neutron rather than a neutron.
 

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  • #2
phinds
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There is an assumption in cosmology say that there is another universe Composed of antiparticles?
I mean that the atom composed of positron rather than an electron, anti-proton rather than a proton and anti-neutron rather than a neutron.
No, there are highly speculative theories regarding that kind of thing but no such assumption.
 
  • #3
mathman
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The problem that has not been solved is why matter exists? Big bang led to a lot of energy, where photons can split into matter and antimatter pairs. Why is there an excess of matter?
 
  • #4
Grinkle
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The problem that has not been solved is why matter exists? Big bang led to a lot of energy, where photons can split into matter and antimatter pairs. Why is there an excess of matter?

A boring (because I think its untestable) proposal might be that its anthropic.

The early universe was infinite in extent, there are many post-expansion regions where complete annihilation took place and some regions where either anti-matter or matter (by chance) pre-dominated. We can only exist in one of those areas, and we will name the region where we exist as "matter", not "anti-matter", because we can't completely shed the human pre-disposition to believe we are special.

Are there models that eliminate such conjecture by showing that large areas of either matter or anti-matter occurring by chance in an infinite universe are not possible?
 
  • #5
mathman
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A boring (because I think its untestable) proposal might be that its anthropic.

The early universe was infinite in extent, there are many post-expansion regions where complete annihilation took place and some regions where either anti-matter or matter (by chance) pre-dominated. We can only exist in one of those areas, and we will name the region where we exist as "matter", not "anti-matter", because we can't completely shed the human pre-disposition to believe we are special.

Are there models that eliminate such conjecture by showing that large areas of either matter or anti-matter occurring by chance in an infinite universe are not possible?
It seems highly unlikely, since these particles are created in pairs, so it is hard to see how they could separate on a large scale.
 
  • #6
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No, there are highly speculative theories regarding that kind of thing but no such assumption.
A boring (because I think its untestable) proposal might be that its anthropic.

The early universe was infinite in extent, there are many post-expansion regions where complete annihilation took place and some regions where either anti-matter or matter (by chance) pre-dominated. We can only exist in one of those areas, and we will name the region where we exist as "matter", not "anti-matter", because we can't completely shed the human pre-disposition to believe we are special.

Are there models that eliminate such conjecture by showing that large areas of either matter or anti-matter occurring by chance in an infinite universe are not possible?
believe me, I don't know
 
  • #7
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Big bang led to a lot of energy, where photons can split into matter and antimatter pairs.

According to our best current model, the Big Bang happened at the end of inflation, and the reheating process that took place then put lots of energy into all of the Standard Model particles, not just photons. The current matter in the universe was not created by photons creating matter-antimatter pairs; it is what's left over after all of the particle-antiparticle pairs that could annihilate as the temperature went down, did annihilate. The reason we still have matter in our universe is that, when that annihilation took place, there was an excess of about one part in a billion of particles over antiparticles; so about one matter particle for every billion photons remained after the annihilation was complete.

The unresolved question is where that one part in a billion excess of matter particles came from: was it put there by the reheating process that took place at the end of inflation? (And if so, why?) Or did it develop because there are high energy processes, not currently included in our Standard Model of particle physics, that favor matter over antimatter instead of being symmetric between them? (And if so, what are those processes and how can we extend our models of particle physics to incorporate them?)
 
  • #8
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It seems highly unlikely, since these particles are created in pairs

As stated in my previous post, your underlying assumption here, that the matter in our current universe was created as particle-antiparticle pairs from photons, is not correct.

We don't know enough about whatever process created the one part in a billion excess of matter in our universe to tell whether it is possible that there are other "universe" regions which had an excess of antimatter over matter instead.
 
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  • #9
The propositions put forth in posts #4 and #7 are not borne out by observations of the microwave background radiation.
 
  • #10
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As stated in my previous post, your underlying assumption here, that the matter in our current universe was created as particle-antiparticle pairs from photons, is not correct.

We don't know enough about whatever process created the one part in a billion excess of matter in our universe to tell whether it is possible that there are other "universe" regions which had an excess of antimatter over matter instead.

The Universe obviously has a baryon asymmetry, but what about the conservation of charge? Is there an equal amount of plus/minus charge in the Universe?
 
  • #11
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The propositions put forth in posts #4 and #7 are not borne out by observations of the microwave background radiation.

Please give more details and references; I don't understand what you are referring to here.
 
  • #12
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Is there an equal amount of plus/minus charge in the Universe?

As far as we can tell, yes, the universe (or at least the part that we can observe) is electrically neutral.
 
  • #13
DAH
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If the early universe created one more anti-matter in a billion over matter, then would stars, planets and life still evolve with opposite charges within atoms?
 
  • #14
phinds
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Hi
If the early universe created one more anti-matter in a billion over matter, then would stars, planets and life still evolve with opposite charges within atoms?
Exactly. We would just call it matter since as has already been pointed out, the distinction is arbitrary anyway.
 
  • #15
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Exactly. We would just call it matter since as has already been pointed out, the distinction is arbitrary anyway.
Well, the distinction is arbitrary up to interacting with stars, planets and life of opposite charge; exchanging space probes, trading cards and letters, and handshakes leads to annihilation... :)
 
  • #16
phinds
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Well, the distinction is arbitrary up to interacting with stars, planets and life of opposite charge; exchanging space probes, trading cards and letters, and handshakes leads to annihilation... :)
No, we would call whatever world we lived in matter and the other stuff anti-matter, just like we do now. It's just words. The anti-matter would, as you say annihilate with our matter.
 
  • #17
Please give more details and references; I don't understand what you are referring to here.
If there were areas where annihilations didn't take place they would show up as anisotropies in the microwave background radiation that just aren't there. Similarly, if there were a vast number of annihilations leaving a small excess of matter particles, the gamma radiation left from the annihilations would show up as a higher radiation excess than observed as the radiation of recombination.
 
  • #18
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If there were areas where annihilations didn't take place they would show up as anisotropies in the microwave background radiation that just aren't there. Similarly, if there were a vast number of annihilations leaving a small excess of matter particles, the gamma radiation left from the annihilations would show up as a higher radiation excess than observed as the radiation of recombination.

Do you have references to support these claims? You appear to be saying that our best current model of the universe is wrong. You need to back up such a claim with strong evidence.

In particular, are you aware that the ratio of photons to baryons has been measured and is about a billion to one? (That is the basis for my statement in post #7 that the excess of matter over antimatter was about one part in a billion.)
 
  • #19
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If there were areas where annihilations didn't take place they would show up as anisotropies in the microwave background radiation that just aren't there. Similarly, if there were a vast number of annihilations leaving a small excess of matter particles, the gamma radiation left from the annihilations would show up as a higher radiation excess than observed as the radiation of recombination.

Do you have references to support these claims? You appear to be saying that our best current model of the universe is wrong. You need to back up such a claim with strong evidence.

In particular, are you aware that the ratio of photons to baryons has been measured and is about a billion to one? (That is the basis for my statement in post #7 that the excess of matter over antimatter was about one part in a billion.)

There are slight anisotropies in the CMBR. There has been much publicity about analysis of results from the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck mission that show both expected and unexpected anisotropies in the CMB map. If we would look at the Universe far from our location, we would not see the same concentric cell structure, or a non-homogeneous Universe. There's still much debate regarding this subject, but the CMB map does indeed correlate with plane of the Earth orbiting the Sun. (There's about 250 million light years space between every shell in this picture). If you take a look at the distribution of quasars in the universe there seems to be a "quasar spherical void" roughly one billion lightyears in radius around us. How to interpret these observations? That is not up to me, but they are significant measurements not to be ignored.
 
  • #20
If you take a look at the distribution of quasars in the universe there seems to be a "quasar spherical void" roughly one billion lightyears in radius around us. How to interpret these observations?

How about "accretion rates onto SMBHs in galaxy centers drastically decreased as galaxy mergers become much rarer"?
 
  • #21
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How about "accretion rates onto SMBHs in galaxy centers drastically decreased as galaxy mergers become much rarer"?

Do I understand you correctly that the distribution of quasars have already been irrefutably explained and supported by scientific evidence? That would be interesting, where can I read more about this? And what about the anisotropies of the CMB map?
 
  • #23
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No, you do not :)

Ah OK, so you were just hypothesizing then. I sounded a little bit like you've provided the answer to this proposed observation of which I wasn't aware, but these observations (quasar distribution + CMB anisotropies) will remain a mystery to science.
 
  • #24
phinds
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... these observations (quasar distribution + CMB anisotropies) will remain a mystery to science.
That seems overly pessimistic. Do you really think we will never figure it out?
 
  • #25
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That seems overly pessimistic. Do you really think we will never figure it out?

I meant that they will remain a mystery until now, I didn't mean that they will remain a mystery in the future. But I'm sceptical whether these findings indicate that the Universe has a center (which these spherical CMB anisotropies, and spherical distribution of quasars are implying), but I don't have any other, more plausible, explanation. Hopefully we will find it soon!
 
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  • #26
phinds
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... I'm sceptical whether these findings indicate that the Universe has a center (which these spherical CMB anisotropies, and spherical distribution of quasars are implying),
They do not imply any such thing. There is no center. I think you are confusing the Observable Universe, which DOES have a center of course, with The Universe, which does not.
 
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  • #27
Bandersnatch
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How to interpret these observations? That is not up to me, but they are significant measurements not to be ignored.
I think you're overselling their significance.
In particular
(There's about 250 million light years space between every shell in this picture).
The quantized redshift is like the large-scale structures and voids that sometimes pop up in the literature - for every paper that says they exist, there's another showing them to be artefacts of the statistical methods employed in analysing the data. That does not constitute convincing evidence that periodicity exists, and for anyone not involved in researching this topic is best to ignore it. Same as one ignores any other claim presented with insufficient evidence.
If you take a look at the distribution of quasars in the universe there seems to be a "quasar spherical void" roughly one billion lightyears in radius around us.
That's not what the picture shows (paper, couldn't find the exact source of the figure, but this is the same author and discussion). It suggests a quasar-less sheet-like void, 3 Gpc away (bisecting the picture vertically), not an Earth-centred spherical one.
In any case, look at the date of that paper. I strongly suspect the anisotropy disappeared with further observations (if you can find modern papers on this topic, please post links).

The closest quasar detected so far is well within 1 Glyrs:
https://en.wikipedia.org/wiki/Markarian_231

As for the 'axis of evil' - the mere fact that it is aligned with the ecliptic strongly indicates that it is a local effect, and not an indication of some zany heliocentric cosmology.

All of these are interesting in the 'Where is Waldo' sense - only instead of for the eponymous character, this is searching for boobery in the data.
 
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  • #28
Chronos
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Yes, there are quasars less distant than 1 billion light years as Bandersnatch noted, see also https://www.nasa.gov/feature/goddar...rest-quasar-is-powered-by-a-double-black-hole if wiki is not your cup of tea. The other stuff he mentioned is also more factually consistent than the mythology to which he refers. What we think we know is not necessarily the final word on the reality of deep space and it is certainly possible to produce any number of statistics from data already archived that seem to defy logic. Some people have actually made careers out of parading the dog faced boys of cosmology before the gullible. Objective and responsible researchers just roll their eyes at such nonsense. They find the subject uncomfortable; not because of any whitewash conspiracy, but, because it's not easy to engage in s*** slinging without some of it sticking to you.
 
  • #29
Do you have references to support these claims? You appear to be saying that our best current model of the universe is wrong. You need to back up such a claim with strong evidence.
I'm not making any claims, I'm merely posing questions that need to be addressed if we are to have a full understanding of the origin of the universe.

In particular, are you aware that the ratio of photons to baryons has been measured and is about a billion to one? (That is the basis for my statement in post #7 that the excess of matter over antimatter was about one part in a billion.)
Yes, I'm aware, and I have no objection to your statement. I was merely pointing out that there should be an artifact of the gamma rays produced during the era of annihilation and there isn't. If you're suggesting that the photon to baryon ratio is a product of the era of annihilation as opposed to the era of recombination, then we should also see a separate remnant from the era of recombination. (By the way, if the microwave background radiation is due to recombination then it shouldn't be considered as thermal blackbody radiation, but rather as a redshifted lyman alpha emission line!)
 
  • #30
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I was merely pointing out that there should be an artifact of the gamma rays produced during the era of annihilation

No, there shouldn't. The photons produced during annihilation have redshifted during the intervening time; their present temperature is the temperature of the CMB, because those photons are the CMB. See below.

we should also see a separate remnant from the era of recombination

No, we shouldn't. Recombination did not produce photons; it just drastically increased the mean free path of photons that already existed.

More precisely, before recombination, photons were constantly being created as electrons and nuclei combined into atoms, and then destroyed as they hit atoms just formed and split them apart again. The net effect was a constant photon number. Recombination simply established that constant photon number as free-traveling photons in a transparent universe, rather than an average of constant creation and destruction in an opaque universe.
 
  • #31
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It suggests a quasar-less sheet-like void, 3 Gpc away (bisecting the picture vertically), not an Earth-centred spherical one

Quasars are the most distant objects discovered by astronomers in the Universe. The peak epoch of quasar activity in the Universe corresponds to redshifts around 2, or approximately 10 billion years ago. An extreme redshift could imply great distance and velocity, but could also be due to extreme mass, or perhaps some other unknown laws of nature. The most distant quasar yet spotted sends its light from the Universe’s toddler years. existed when the universe was only 690 million years old, right when the first stars and galaxies were forming.

My point: if you observe quasars (that represent the Universe's toddler years) in the centers of the most distant galaxies in all directions, then how does this not make us the center?
 
  • #32
Bandersnatch
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My point: if you observe quasars (that represent the Universe's toddler years) in the centers of the most distant galaxies in all directions, then how does this not make us the center?
You observe them also in centres of relatively nearby galaxies in all directions. But I think you're asking why do they peak in activity at roughly the same distance?
Because, as you say, these are the objects associated with the early history of the universe. It is then a simple consequence of the finite speed of light that you see things that happened during the 'toddler years' far away and at roughly the same distance all around you.
This is much the same as how all observers see the CMBR as centred around each of them. It makes you the centre of your observable universe only. Any other observer elsewhere in the universe is expected to see a similar distribution of quasars.
I believe it has been alluded to by others in this thread already.


Also, can you be clearer about attribution of the bits you're quoting from other articles (and how they're relevant)? In the paragraph above I can see sentences copied from the Wikipedia article, and from Science News (unattributed).
At least put them in quotation marks. Otherwise it's hard to tell where you're making your own points, and where you're providing sources in support of those points.
Thanks.
 
  • #33
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You observe them also in centres of relatively nearby galaxies in all directions

This is true for galaxies nearby, but a galaxy far away from us, say in between us and our observable Universe, isn't seeing the same distribution of quasars in all directions, right? Or is the distribution of quasars, just like the CMB anisotropy, distributed the same way for every galaxy?
 
  • #34
Bandersnatch
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but a galaxy far away from us, say in between us and our observable Universe, isn't seeing the same distribution of quasars in all directions, right?
It should be the same, yes. For the reasons given above. I.e., every (comoving) observer sees the universe at the same age, so every age-dependent distribution should be the same.
 
  • #35
phinds
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Or is the distribution of quasars, just like the CMB anisotropy, distributed the same way for every galaxy?
Yes, it's the same no matter where you are in the universe. Again, there is no center.
 

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