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DE & DM BB product or post-BB?

  1. Aug 1, 2006 #1
    The universe is now 73% Dark Energy, 23% Dark Matter, and 4% matter. Have these percentages changed during the ~13billion years since the big bang ended? I wonder if DE and DM are big bang products, or are they products of a post-BB process?

    Is there any evidence from WMAP or any source giving an answer to this question? I thought galaxy rotation curves of highly redshifted distant galaxies might tell us if the DM percentage has changed over the history of the universe, but then I calculated that we cant see galaxies far enough away to tell if the DM percentage was smaller in an earlier time of the universe...
     
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  3. Aug 1, 2006 #2

    marcus

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    bear in mind that we dont know for sure that DM and DE exist.
    it might eventually be possible to get rid of them and explain their effects using a modification of the law of gravity

    but suppose for sake of discussion that they do exist and behave the way they are supposed to in the usual "LambdaCDM" picture. In that picture Lambda is a constant and accordingly the DE density is a constant.

    then no new DM and matter are being created, but DE has a CONSTANT DENSITY---the same throughout all space and time-----so when a sample volume of space expands it contains more DE

    So to answer your first question.

    YES the percentages have changed in an entirely predictable way! Think of an arbitrary mass/energy unit say equal to the mass of some beautiful supercluster if you like. Say the Virgo supercluster---some arbitrary unit of mass'energy that appeals to you. Imagine a volume of space that, at present, contains:
    4 units of matter
    23 units of DM
    73 units of DE.

    Now travel to a future time when that volume will have DOUBLED IN VOLUME. It now contains:
    4 units of matter
    23 units of DM
    146 units of DE.

    Therefore the percentages have CHANGED. You can work them out. The fractional parts are:
    4/173 matter
    23/173 DM
    146/173 DE

    As we speak, the percentage of DE in the universe is slowly increasing and the other two percentages are declining.
    =====================
    Just for fun, let's travel back to a time when this sample volume was only ONE HUNDREDTH the volume it is today. then it would contain
    4 units of matter
    23 units of DM
    0.73 units of DE (which I'll round up to 1.0 for convenience.)

    For a total of about 28 units. So the fractional parts (to convert to percentage) would be about
    4/28 of the total is matter
    23/28 of the total is DM
    1/28 of the total is DE.

    So back then, which was sort of at redshift 4 (not all that long ago or far away) the universe was NOT dominated by DE as it is today. It was MATTER DOMINATED. in fact 27/28 of the mass'energy in it was matter.
     
    Last edited: Aug 1, 2006
  4. Aug 1, 2006 #3

    wolram

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    Here is a hint that the (axion) may be a reality.

    http://www.scientificamerican.com/a...&articleID=0006BA85-FC58-1492-BAAC83414B7F000

    Named after a laundry detergent and originally proposed to clean up a problem with particle physics, axions are curious critters. Axions produced during the big bang could be lurking all around us, contributing to the dark matter that constitutes 22 percent of the universe. Other axions, freshly formed inside the sun, could be streaming through us. And according to a paper published in March, laboratory-made axions might have been detected for the first time by an experiment in Italy known as PVLAS (polarization of the vacuum with a laser).
     
    Last edited: Aug 1, 2006
  5. Aug 2, 2006 #4
    I have heard of axions, neutralinos, etc, but never saw a chart of where they fit into standard model, so I am only famliar with the 3 leptons & 6 quarks. Thanks Wolram, at least now I know axions are electrically neutral and lighter than neutrinos. (Do you know of any charts putting any of the new particles into place? :)

    Marcus, what you say about DE agrees with what I have read. But when reading, sometimes its hard to tell how much evidence is backing up the statements, so its good to hear from someone who gives a balanced opinion.

    How far away is redshift 4? I have read that we can observe galaxies 1/2 billions light years away, that is only going back 4% of the lifetime of the universe. When I started this thread, I hoped to propose that studying galactic rotation curves of galaxies over 1 billion lightyears away, would tell us whether DM is also growing, along with DE. But I dont know if we can see that far yet.

    I havent heard of any BB theory that accounted for DM or DE, my understanding is we are still trying to fit DM & DE into the BB picture. The thing that bothers me about DM & DE, is, they are both such a huge portion of our universe, neither are predicted by BB - Wouldnt a single solution that manifested as DM & DE be more elegant than 2 independant entities that managed to somehow dominate the universe? That is why I am interested in measuring the DM ratio in the early times of the universe.

    Marcus, I have done calculations similar to yours, but I said what if DM has a relationship with DE, and has also grown over time? If you go back to 1/2 the age of the universe, then DM should at that time be only 1/8 ( 1/2 cubed) the current quantity. The current 23% * 1/8 = ~3%... I find it extremely interesting "coincidence" that the age of quasars ended at the same time that the quantity of DM exceeded the quantity of matter in the universe (Not stating this as fact, of course, just as a possibility worth looking into?). Perhaps the quasars were "fuel-starved" when DM cancelled out their gravitational suction of deep-space hydrogen? For that matter, how could quasars fuel their brilliance for 8 billion years if DM had the same gravity-cancelling effect it currently does on galaxies? :(

    So to turn all this into a question...
    What is the evidence that DM is constant
    and are there any theories that allow DM to grow over time?
    Or is long-distance repulsive gravity a more serious contender than DE & DM?
     
  6. Aug 2, 2006 #5

    marcus

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    I cant personally guarantee a balanced opinion. Pay careful attention to what others say (SpaceT, hellfire, Garth, etc...) to get balance.
    I don't actually believe in DE and am doubtful about DM. To me the evidence looks like instead of different kinds of matter and energy fields we need a MODIFICATION OF THE LAW OF GRAVITY, that is a slight modification of Gen Rel. Hopefully something that we can test within the solar system context. I am more interested in MOND proposals.

    Google "Ned Wright" and use his cosmology calculator. Hellfire has programed his own version of the calculator. Every cosmologist needs one.

    http://www.astro.ucla.edu/~wright/CosmoCalc.html

    That bothers me too. I think it bothers professional cosmologists. Look up "J Moffatt" and "Bekenstein" on ARXIV.ORG.
    They are the main people working on MODIFIED GRAVITY today.
    Often people use the abbreviation "MOND" which goes back to work by M. Milgrom in the 1980s. You can do keyword on MOND as well as "modified gravity", to find other authors.

    personally I think that if dm and de actually existed they would have to be different fields or substances because DE DOES NOT CLUMP and DM CLUMPS, so I guess that it is useless to try to explain them by a single substance

    However it would be even more elegant to explain the EFFECTS of DM and DE by a single modification of Gen Rel. A goal could be to find a SINGLE modification that causes the effects of BOTH. And the proposed new law of gravity would also have TESTABLE CONSEQUENCES that one could look for here at home in the solar system.

    this is what I see suggestions of, in the most recent papers of Moffatt I have read, and also in the most recent paper of Bekenstein.

    I believe that one can look at galaxies of many different ages, from different time periods. And my understanding is that mature spiral galaxies all need about the same addition of DM to be assumed so that their rotation curves will compute right. I don't think anyone has seen a TREND for the DM fraction of galaxy masses to change over time. However this would be good to check with some of the other people here.

    If you ever want to check out articles on relativistic MOND, or modified gravity, and need help searching ARXIV.ORG then just ask. I will be glad to get you some links to online articles.
     
  7. Aug 2, 2006 #6
  8. Aug 2, 2006 #7

    marcus

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  9. Aug 2, 2006 #8

    wolram

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  10. Aug 3, 2006 #9
    Thank you everybody!

    Wolram, exellent Wiki article!

    Marcus & Matt, thanks for all the excellent links! I'll have to read up on MOND.

    Marcus, I'm very interested if anyone has researched whether DM has grown in proportion with DE. I am pursuing a testable line of thought in that direction. But I can't see how a mod to gravity could explain your puzzle "DE DOES NOT CLUMP and DM CLUMPS" ... Do you have time to elaborate how a gravity or GR mod could accomplish both?

    May I conclude with something completely silly? Has anyone entertained the idea that maybe the nature of spacetime is to grow? Our realm of perception is often useless as a frame of reference for understanding the macroscopic universe. We are accustomed to physical objects not growing in our realm, maybe spacetime as a whole acts differently. We have already admitted as much with terms like Vacuum Energy and Dark Energy - forces that seem to produce "something from nothing". For that matter, we understand our universe as resulting from the big bang, but what started the BB? Again something from nothing? (Even the cyclical theories are forced to have a beginning SOMEWHERE!) Sorry to bother you with something so philosophical, and, at the moment, beyond present science. It just popped into my head as a very basic question no one seems to be asking. Hey, if you know of anyone who has put together a good case about it, I'm listening!
     
    Last edited: Aug 3, 2006
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