Big Bang Matter-Antimatter Annihilation

  • Thread starter RJ Emery
  • Start date
  • #1
100
2

Main Question or Discussion Point

In as few words as possible, could someone refresh my memory as to why in the Big Bang there was a slight excess of matter that survived the matter-antimatter annihilation?

And is such matter just baryons, or was there remaining from the annihilation other forms of matter besides baryons?
 

Answers and Replies

  • #2
hellfire
Science Advisor
1,047
1
In as few words as possible, could someone refresh my memory as to why in the Big Bang there was a slight excess of matter that survived the matter-antimatter annihilation?
It is usually assumed that some conditions during baryogenesis lead to this asymmetry. These are known as Sakharov conditions. I cannot expand on this, but only provide you the link to wikipedia: Sakharov conditions.

And is such matter just baryons, or was there remaining from the annihilation other forms of matter besides baryons?
Baryon asymmetry is the one that has to be explained due to observations. After annihilation a rest of baryons survived and a lot of photons were created. The photon to baryon ratio is about 109. These photons are currently in the cosmic microwave background. For other particle families such as leptons or non-baryonic dark matter the abundances of particles and antiparticles might be equal.
 
  • #3
bapowell
Science Advisor
Insights Author
2,243
259
In as few words as possible, could someone refresh my memory as to why in the Big Bang there was a slight excess of matter that survived the matter-antimatter annihilation?

And is such matter just baryons, or was there remaining from the annihilation other forms of matter besides baryons?
As hellfire mentions, the matter/antimatter asymmetry arose during conditions after the big bang. The conditions that would need to exist in order to generate a matter/antimatter asymmetry are known as the Sakharov conditions. In brief, these conditions include particle physics processes that favor matter to antimatter and/or a lack of thermal equilibrium between processes that turn matter into antimatter and processes that turn antimatter into matter. The matter/antimatter asymmetry is seen not only in baryons but also leptons (electrons, neutrinos, etc). It is unknown whether the asymmetry originated in the baryonic sector (and transferred, via interactions) to the leptonic sector or vice versa.
 
Last edited by a moderator:
  • #4
9
0
The elementry pair particle formation is well documented. The remainder of the answer is like most cosmological theories is speculative. It is my way of responding to the question that makes the most sense to me. I have seen other speculations that posit the existance of the positron as traveling into the past sleinad
 
  • #5
BillSaltLake
Gold Member
184
0
It would be sufficient if the only matter-over-antimatter excess was of neutrons (although it is not known whether this is the way it actully happened). One excess neutron per ~billion photons would lead to what we see now. The reason for the excess is still not known.
 
  • #6
bapowell
Science Advisor
Insights Author
2,243
259
The elementry pair particle formation is well documented. The remainder of the answer is like most cosmological theories is speculative. It is my way of responding to the question that makes the most sense to me. I have seen other speculations that posit the existance of the positron as traveling into the past sleinad
You are mistaken. A positron is mathematically equivalent to an electron traveling into the past.
 
  • #7
However, is the expectation to have equal matter and antimatter is hypothetical or a well proven necessity?
 
  • #8
BillSaltLake
Gold Member
184
0
There is no known mechanism by which the observed imbalance should result. It would be "nice" if an experiment could be done, but it's extraordinarily difficult to replicate conditions at t = 1 microsec. Even if a blackbody cavity at those temperatures could be produced, the walls of the container would destroy many more antiparticles than the signal we would be looking for, causing a false "verification".
 
  • #9
9
0
I would have to say that to say that is the natural state of things. When energy is transformed to matter half the energy become an elementary particle of matter and the other half becomes an elementary particle of anti-matter. Balance is always maintained. That includes equal amounts of matter and anti-matter and, it also maintains the equality of the time associated with the newly formed matter.
As far as expectations are concerned, nothing in cosmology can be lab tested......sleinad
 
  • #10
bapowell
Science Advisor
Insights Author
2,243
259
As far as expectations are concerned, nothing in cosmology can be lab tested......sleinad
Quite the contrary. In cosmology, the universe itself becomes your laboratory. Granted, one does not have the luxury of repeated, controlled experiments. But that's what Bayesian statistics is for. Cosmologists might not be claiming detections at 5 sigma like the particle physics community, but don't be fooled: cosmology is a rigorous science with a sophisticated statistical methodology. We know a tremendous amount about the early universe.
 
  • #11
6,814
12
In as few words as possible, could someone refresh my memory as to why in the Big Bang there was a slight excess of matter that survived the matter-antimatter annihilation?
No one is quite sure. Antimatter/matter asymmetry comes out of some grand unified theories of particle physics, but even then, it looks like someone just added in by hand rather than something nature.

We do know that whatever happened happened before fusion or else elemental abundances would be off. We also know that whatever happened, happened at energies higher than the current particle accelerators, or else we would have seen something at CERN.

We also have lots of limits as to how much antimatter there could be in the observable universe without anyone noticing.

And is such matter just baryons, or was there remaining from the annihilation other forms of matter besides baryons?
Positrons
 
  • #12
9
0
Thank you for that very interesting response.
In meditating on your response, it has just come to my attention that if you follow the initial energy to matter transformation, no matter what theory you believe in, an elementary particle of matter is always accompanied by it’s antiparticle at transformation. This is the way it always occurs in laboratory particle accelerators. Every particle of matter in our universe had to be transformed in the same manner.
There must be a cosmic balance sheet. In every transformation, every elementary particle is accompanied by it’s antiparticle, every charge is accompanied by it’s opposite and, that must follow for time also since, it is also part of the transformation. If there is such a balance sheet, then, that balance should also operate for annihilations.
Such a balance would not permit any asymmetry to exist between matter and antimatter.
Thank you bapowell for bringing this to my attention.....sleinad
 
  • #13
bapowell
Science Advisor
Insights Author
2,243
259
In every transformation, every elementary particle is accompanied by it’s antiparticle, every charge is accompanied by it’s opposite and, that must follow for time also since, it is also part of the transformation. If there is such a balance sheet, then, that balance should also operate for annihilations.
Yes, but it is supposed that such a balance sheet is not honored by certain particle interactions. The idea is that grand unified theories include interactions for which particles are not always accompanied by their antiparticle. If these interactions were operative in the early universe before the grand unified symmetry was broken, a matter/anti-matter asymmetry could be generated.
 
  • #14
BillSaltLake
Gold Member
184
0
It is possible to create two neutrons (= total baryon number of 2) from a system with zero initial baryon number (e.g., an equal # of neutrons & antineutrons, etc.).
 
  • #15
9
0
Is there really a reliable GUT model? I have a hard time accepting data from theories whose interactions cannot be verified. The composition of the present universe has been computed from data gathered by the space telescope. Only 4%of it consists of normal matter with only 1/10 (0.4%) of that total being visible matter like our sun. Most of that, 3.6% consists of is interstellar gas more complex than hydrogen with only 1/10 of that existing as elements more complex than hydrogen. The remainder of the universe is supposedly 73% dark energy and 23% dark matter.
Before the beginning, the universe must have consisted of a limitless space which was evenly permeated with dark energy. After the beginning until now, the universe went from 100% dark energy to the it’s present diversity.
How did the original consistency of the universe get transformed to that of the present? The present distribution does suggest the route that the transformation had to take. First some of the dark energy is transformed into dark matter. This continues until the density of the dark matter reaches a point where some of it can actually interact and be transformed into composite particle of visible matter. This type of step transformation does not suggest something sudden like a Big Bang which would seem to bypass the dark matter stage. What it does suggest, is a slow gradual type of transformation.
Sorry bapowell it takes me more time to extract logical responses these days. Some of data are extracted from ana article previously published in another science forum and which I have just published as a new thread in this forun. It is called “Micro-pops not Big Bang”. You might be interested to seem how I have presented some of my deductions which I do not swear that are completely correct. I am now working on an updated version that tries to bring these deductions up to date relative to the responses I have had.....sleinad
 
  • #16
bapowell
Science Advisor
Insights Author
2,243
259
First some of the dark energy is transformed into dark matter.
Statements like this require substantiation. As it stands, it is pure speculation and against forum rules.

I have presented some of my deductions which I do not swear that are completely correct. I am now working on an updated version that tries to bring these deductions up to date relative to the responses I have had.....sleinad
It is good that you are interested in gaining an understanding of the working of the universe, however, this is not the place to present your ideas. We discuss mainstream science here at PF.
 
  • #17
9
0
quote by bapowell
We discuss mainstream science here at PF.

Response
I was so happy that I thought I had been having discusssions with individual in the ionosperic region of the scientific world. Sorry that I have strayed into the lower mainstream regions.....sleinad
 
  • #18
phinds
Science Advisor
Insights Author
Gold Member
2019 Award
15,897
5,559
quote by bapowell
We discuss mainstream science here at PF.

Response
I was so happy that I thought I had been having discusssions with individual in the ionosperic region of the scientific world. Sorry that I have strayed into the lower mainstream regions.....sleinad
If by "ionosperic [sic]" you mean "unsubstantiated speculation" then yes, you are in the wrong place. As bapowell said, this forum is for mainstream science.
 
  • #19
9
0
quote by bapowell
It is good that you are interested in gaining an understanding of the working of the universe, however, this is not the place to present your ideas. We discuss mainstream science here at PF.

quote by phinds
If by "ionosperic [sic]" you mean "unsubstantiated speculation" then yes, you are in the wrong place. As bapowell said, this forum is for mainstream science

Response
Dear members of the Physics Forum
I am 81 years old and there was never a moment in my life when I thought that I knew everything. Thus, I’m still open to learn anything. If my thoughts had already calcified, I would not have needed to join a forum. Of all the sciences I have studied, Physics had the most mysteries that interested me. That was why I joined this forum.
The word “unsubstantiated” does not fit into science. The word “speculation” does. That is how science starts, with speculation. After that comes the attempts at substantiation.
Forums are about discussion groups who are attempting to make advances or resolve inconsistencies in certain fields. They should not be used to stifle them........sleinad..
 
  • #20
6,814
12
Is there really a reliable GUT model?
No there isn't.

I have a hard time accepting data from theories whose interactions cannot be verified.
Same here. However, the limits on the amount of anti-mater in the universe don't come from theory but from observation. There are very strong limits on the amount of anti-matter that there could be before weird stuff happens.....

http://prl.aps.org/abstract/PRL/v84/i17/p3756_1
http://www-conf.slac.stanford.edu/ssi/2011/Muller_072611.pdf
http://arxiv.org/abs/0808.1122

Before the beginning, the universe must have consisted of a limitless space which was evenly permeated with dark energy. After the beginning until now, the universe went from 100% dark energy to the it’s present diversity.
Dark energy works the other way. When the universe is dense, dark energy doesn't have much of an effect. As the universe becomes less dense, it has more influence.

It is called “Micro-pops not Big Bang”. You might be interested to seem how I have presented some of my deductions which I do not swear that are completely correct. I am now working on an updated version that tries to bring these deductions up to date relative to the responses I have had.....sleinad
It might help to read some intro books on cosmology so that you familiarize with all of the observations that are out there. The problem with "no big bang" is that you can see the big bang.
 
  • #21
phinds
Science Advisor
Insights Author
Gold Member
2019 Award
15,897
5,559
... It might help to read some intro books on cosmology so that you familiarize with all of the observations that are out there. The problem with "no big bang" is that you can see the big bang.
:rofl:

You make SUCH a good point. Not likely to have any effect, but a good point non the less.
 
  • #22
9
0
—Quote from twofish-quant---
However, the limits on the amount of anti-mater in the universe don't come from theory but from observation. There are very strong limits on the amount of anti-matter that there could be before weird stuff happens...
—End quote---
How can anti-matter be distinguished from regular matter at a distance? Is there some signature that can differentiates the two? I’m asking this because you mentioned the limits of the amount of anti-matter observed......sleinad
 
  • #23
9
0
–start of quote--
The problem with "no big bang" is that you can see the big bang.
–end of quote–
Do you mean by ‘seeing the big bang’ that you are looking at the afterglow or microwave radiation supposedly representing the remains of the “Big Bang”? I thought that the predicted galactic shadow obscuring that microwave radiation that should have verified the occurence of the “Big Bang” did not come off very well......sleinad
 
  • #24
bapowell
Science Advisor
Insights Author
2,243
259
I thought that the predicted galactic shadow obscuring that microwave radiation that should have verified the occurence of the “Big Bang” did not come off very well......sleinad
You are mistaken. Foregrounds can be accurately subtracted from CMB maps. See http://lambda.gsfc.nasa.gov/product/foreground/. Browse the rest of this site to see the cleaned maps together with the results of extensive analyses carried out by the WMAP team.

But even if the galactic foregrounds could not be adequately subtracted, the CMB is still there. The big bang happened.
 
  • #25
6,814
12
How can anti-matter be distinguished from regular matter at a distance? Is there some signature that can differentiates the two? I’m asking this because you mentioned the limits of the amount of anti-matter observed......sleinad
When anti-matter hits matter you get specific radiation signature. We know for example, that something is generating anti-matter at the core of the Milky Way. One thing about anti-matter is that it's not particularly mysterious, people make anti-matter all the time, and there are a lot of processes that are known to generate anti-matter.

Since we don't see this signature, we can limit the amount of possible anti-matter in the universe. The limits aren't zero, but they are pretty low, and as our detectors improve, they are always getting lower, and if you want to argue for cosmological amounts of antimatter it's really, really difficult to come up with something that works. The Loch Ness monster and bigfoot might exist, but it's hard to argue that they live in Times Square.

There's also limits from big bang nucleosynthesis. Even small amounts of antimatter are going to wildly change the nuclear reactions that create helium and other light elements, and that's going to be easily detectable.
 

Related Threads for: Big Bang Matter-Antimatter Annihilation

Replies
2
Views
506
  • Last Post
2
Replies
41
Views
3K
Replies
8
Views
836
  • Last Post
Replies
5
Views
954
Replies
5
Views
1K
Replies
8
Views
807
  • Last Post
3
Replies
51
Views
9K
Top