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Lambda as black hole buster

  1. Jan 22, 2012 #1

    marcus

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    Evidence has been mounting that cosmic acceleration behaves as if simply due to a constant of nature Lambda, a small intrinsic curvature term (reciprocal area) which appears naturally in the Einstein equation.

    For more about this, google "prejudices against constant" and have a look at the top hit:
    http://arxiv.org/abs/1002.3966
    Why all these prejudices against a constant?

    However in extreme circumstances some physical constants appear to "run"--that is change with radically increasing energy or decreasing scale. One approach to quantum gravity, the Asymptotic Safety approach, suggests that Lambda may increase with increasing energy, or energy density.

    So what would happen to black holes if you could increase Lambda? Intuitively they should lose mass, dwindle down to nothing. Can we get a handle on this?

    Here's a paper that was published in Physical Review Letters in 2004:
    http://prl.aps.org/abstract/PRL/v93/i2/e021102
    Their premise, namely "big rip" from "phantom dark energy" has gone somewhat out of style with researchers since it seems more and more likely that Lambda is just a curvature constant of nature (not some evolving "energy" field). But we can still look at their analysis and conclusions. Here is the preprint:
    http://arxiv.org/pdf/gr-qc/0402089v3.pdf

    I found another more recent paper along related lines. This time it is a 2010 paper by Maurice van Putten at the Uni Orléans:
    http://arxiv.org/abs/1003.0604
    Extended black hole cosmologies in de Sitter space
    He derives a bound on BH mass which is proportional to the inverse square root of Lambda.

    I haven't made a thorough search by any means.

    It does seem that, as one would intuitively expect, as you increase Lambda it restricts what mass a BH can retain and black holes must eventually shrink.
    An unbounded increase in Lambda (as when the fixed point is approached in Asymptotic Safety QG) would wipe out black holes.

    Any comments?
     
    Last edited: Jan 22, 2012
  2. jcsd
  3. Jan 22, 2012 #2
    Let's fast forward events to the point where virtually everything is locked up in numerous black holes. A question that might reveal something is to wonder what might occur if all that matter/energy were released. The universe by this time would be extraordinarily vast, even compared to today. Is the answer nothing? Mini-universes, starting fresh? It presents an interesting path to multiverses, where they are the product of a much older universe that underwent expansion, tore open all its resulting black holes and birthed mirad new universes, of which we are one.
     
  4. Jan 22, 2012 #3

    marcus

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    It's a provocative vision, I can see how it could be very appealing. But the typical path we follow here is to hew close to the line of professional research using mainstream models.

    So the question I would naturally ask is how do you see "virtually everything is locked up" in black holes?

    What mechanism would achieve that? Do you have a source? I see no physical reason why everything should eventually fall into a black hole, given our standard model Lambda CDM universe.

    BTW Lawrence Krauss has an article http://arxiv.org/abs/0704.0221 which includes some vision of the standard model LCDM's longrange future. It's kind of interesting and he is both a good writer and good cosmologist. Of course new physics could intervene but useless to speculate until some hint of WHAT new physics shows up.
     
    Last edited: Jan 22, 2012
  5. Jan 22, 2012 #4

    phinds

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    Not only does it seem, as Marcus points out, unlikely that everything would get locked up in black holes, since there's just no reason for that to happen, even it you DID postulate that situation and then say they evaporated / blew up / whatever, there would not be enough local matter anywhere to do much and CERTAINLY not enough to "start a new universe"
     
  6. Jan 22, 2012 #5

    marcus

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    My hunch is you're right, seems reasonable. Also what stands out for me is that all the evidence is that Lambda is NOT DESTINED TO INCREASE in our future. The observations suggest that it is constant. The Asym Safe QG scenario which has been gaining notice and credibility suggests that Lambda could have been large around time of our "big bang" or "big bounce" and would have been decining as distances expanded. Just the opposite of the kind of behavior imagined. So more likely to DECREASE or remain constant in our future.

    However kind of interesting that, in a cosmological bounce, Lambda could be expected to bust up any black holes that had formed in the previous contracting universe.
    There's a lot of research literature on bounce cosmology. This may have a bearing on one or more issues.
    As a sample here's a bunch of Loop quantum cosmology papers ranging from 2008 to the present. In this treatment, quantum corrections make gravity repellent at extreme high density, forcing a bounce. According to Lqg model the "big bang" MUST be preceded by a contracting phase. It's basically what the papers are about:
    http://inspirehep.net/search?ln=en&...2y=2011&sf=&so=a&rm=citation&rg=50&sc=0&of=hb
     
    Last edited: Jan 22, 2012
  7. Jan 22, 2012 #6
    I have few layman's questions, if somebody cares to answer.

    1. How can Lambda be small intrinsic curvature? I take that you mean spacetime curvature, not space curvature. Shouldn't space and time evolve according to the presence of matter and energy in it? I mean, pre-curved spacetime doesn't sound right to me, because you can ask what is curving it? Just my rambling...

    2. How can there ever be a bounce, when universe appears to accelerate?

    3. Is unbounded increase in Lambda responsible for inflation?
     
  8. Jan 22, 2012 #7
    funny how i talked about something similar to this last night but got my thread deleted because i had too much "imagination" and that i should go on a sci-fi forum.

    Anyways interesting stuff ill follow up on the links
     
  9. Jan 22, 2012 #8
    I never actually stated this would be in our future, recognising that anything this full blown could not be made from the disgorging of any black hole currently known. I was only suggesting that the idea could have already happened from a far more massive universe prior to ours.

    As to the question of how almost everything ends up in a blackhole. /shrug. When I say fastforward, I usualy think in terms of trillions of years. Given the rate at which galactic black holes are considered to consume material (I think 1 sun a year is a figure I saw on this board) I make an assumption that in time, a galaxy will end up entirely within a black hole, purely as a losing, gravity-driven battle.

    Honestly, the thing I'd like to focus on is this: the big bang banged. It had all matter/energy and space tied up in a rediculously dense ball of some equally rediculously small dimension and yet something forced it apart. So what's to stop a black hole, like the one at our galaxtic center 'going off'?

    PS Galaxtic? Galactic? Galaqtik...
     
  10. Jan 22, 2012 #9
    The fascinating thing about that article is these assumed future cosomologists, who will have the easiest job in the universe, will inevitably be unable to discern the true origin of their universe and won't even know it. They will become Flatlanders.
     
  11. Jan 22, 2012 #10

    phinds

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    Well, maybe. You state as fact a concept which is just one of the models, and I believe NOT the favored one, which is that the universe started off infinite in size and thus is still infinite in size. Even if it started off finite in size, however, we have no evidence that it was SMALL in size, only that it was staggeringly dense.
     
  12. Jan 22, 2012 #11
    I'm in favour of finite and unbounded. When I said small dimension, I was envisioning statements such as the early universe fitting into a pea or a grapefruit. That sort of thing. I keep meaning to calculate how many cricket balls you can fit in a circle 3km across.

    Also, since the current density is guesstimated at 5.5 hydrogen atoms per cubic meter, I'm gonna go ahead and say the universe would have had to be far more spatial compact than it is today in order to be staggeringly dense.
     
  13. Jan 23, 2012 #12
    It is possible that the acceleration phase is temporary. For example, if the cosmological constant is actually *negative*, it will eventually re-collapse, yet still exhibit an accelerating epoch.
     
  14. Jan 23, 2012 #13

    Drakkith

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    The consumption of a black hole depends on the conditions at the center of each galaxy. Unless something causes most of the galaxy to spiral inward, galactic black holes will run out of material around them in time.

    We don't know why the universe expanded from it's initial conditions at the time of the big bang. Given the current state of the universe that we can observe, there isn't any known force that could have caused it, especially Lambda as it currently is. I expect that to know what happened, and what happens inside of a black hole would require a quantum theory of gravity or something similar.

    As to what stops a black hole from doing the same, I'd have to say it's the fact that it isn't the Big Bang.
     
  15. Jan 23, 2012 #14

    Drakkith

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    Depends on what you mean by "possible". Generally most people use it to say that something CAN happen, but they have no idea if it will happen. For example, I can say that it's possible that a meteor will fall on my head tomorrow. Will it happen? Only if there is already a meteor on the correct trajectory and at the right distance to fall on my head tomorrow.

    On the other hand, if you ask me is it possible that the gravitational constant will reduce by half tomorrow, I would have to honestly say I have no idea, because I cannot see the future. Do I have any reason to believe it will? Not at all.

    So is it possible the acceleration phase is temporary? Maybe.

    Edit: For the record, I initially thought you asked "IS it possible". Hence my answer above. I must be tired...
     
    Last edited: Jan 23, 2012
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