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Big Bang Matter-Antimatter Annihilation

  1. Mar 12, 2007 #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?

    And is such matter just baryons, or was there remaining from the annihilation other forms of matter besides baryons?
     
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  3. Mar 12, 2007 #2

    hellfire

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    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.

    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.
     
  4. Dec 28, 2011 #3

    bapowell

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    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: Dec 28, 2011
  5. Dec 28, 2011 #4
    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
     
  6. Dec 28, 2011 #5

    BillSaltLake

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    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.
     
  7. Dec 28, 2011 #6

    bapowell

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    You are mistaken. A positron is mathematically equivalent to an electron traveling into the past.
     
  8. Dec 29, 2011 #7
    However, is the expectation to have equal matter and antimatter is hypothetical or a well proven necessity?
     
  9. Dec 29, 2011 #8

    BillSaltLake

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    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".
     
  10. Dec 29, 2011 #9
    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
     
  11. Jan 3, 2012 #10

    bapowell

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    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.
     
  12. Jan 4, 2012 #11
    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.

    Positrons
     
  13. Jan 4, 2012 #12
    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
     
  14. Jan 4, 2012 #13

    bapowell

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    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.
     
  15. Jan 4, 2012 #14

    BillSaltLake

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    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.).
     
  16. Jan 5, 2012 #15
    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
     
  17. Jan 5, 2012 #16

    bapowell

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    Statements like this require substantiation. As it stands, it is pure speculation and against forum rules.

    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.
     
  18. Jan 6, 2012 #17
    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
     
  19. Jan 6, 2012 #18

    phinds

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    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.
     
  20. Jan 6, 2012 #19
    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..
     
  21. Jan 9, 2012 #20
    No there isn't.

    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

    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 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.
     
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