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Vilenkin claims to have refuted the CNS conjecture

  1. Oct 4, 2006 #1

    marcus

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    http://arxiv.org/abs/hep-th/0610051
    On cosmic natural selection
    Alexander Vilenkin
    4 pages

    "The rate of black hole formation can be increased by increasing the value of the cosmological constant. This falsifies Smolin's conjecture that the values of all constants of nature are adjusted to maximize black hole production."

    what do you think? did he succeed?

    his argument involves black holes coming into existence by a "quantum fluctuation"
    at one point he invokes SOLAR MASS black holes coming into existence by quantum fluctuation

    I think it's great that folks like Vilenkin (prominent, Hawking-co-author etc) are sufficiently uncomfortable about CNS that one of them should try to argue it away. And also I appreciate the great lengths and effort that Vilenkin went to in the attempt.

    It is all to the good. Also will force Smolin to be more specific about the "rate of black hole formation", which was always left a bit vague IIRC
     
    Last edited: Oct 4, 2006
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  3. Oct 4, 2006 #2

    marcus

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    here is stuff about Vilenkin
    http://en.wikipedia.org/wiki/Alexander_Vilenkin
    http://www.edge.org/3rd_culture/bios/vilenkin.html

    103 arxiv papers
    http://arxiv.org/find/grp_physics/1/au:+Vilenkin/0/1/0/all/0/1

    it is great that someone of his stature is trying to dispose of CNS!


    also, here is another piece of good news. Carr's Cambridge Press collection of essays called Universe or Multiverse? is finally coming out. According to Vilenkin it is in press

    look at his citations:
    [1] Universe or Multiverse, ed. by B.J Carr (Cambridge University Press, Cambridge, in press).
    [2] L. Smolin, Class. Quantum Grav. 9, 173 (1992).
    [3] L. Smolin, The Life of the Cosmos (Oxford University Press, 1997).
    [4] L. Smolin, in [1], arXiv:hep-th/0407213.

    Smolin's essay "Scientific Alternatives to the Anthropic Principle" is what Vilenkin cites as [4] and is to be one of the chapters in Carr's book.
    so that paper, http://arxiv.org/hep-th/0407213 , is finally going to appear.

    It is the one which evoked notable outbursts from Leonard Susskind.

    it is likely to be a nice constructive controversy :smile:
     
    Last edited: Oct 4, 2006
  4. Oct 4, 2006 #3

    Chronos

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    I think Smolin still has the stronger argument by virtue of including falsifiable predictions in his model. It is unclear if ramping up the cosmological constant is necessarily sufficient to automatically increase black hole formation rates. Assuming an accelerating universe, it implies black hole formation rates should increase proportionate to the rate of expansion. I don't see any practical way to validate this hypothesis given bean counting extragalactic solar mass black holes is not very doable.
     
  5. Oct 5, 2006 #4

    selfAdjoint

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    I haven't read the Vilenkin paper but if his thesis is "Higher CCs imply more black holes, while CNS implies universes evolve to maximize black holes, but our universe is observed to have a small CC, therfore CNS is false". then it misunderstands evolution. That works, whether in biological species or Alife simulation, according to two principles: The struggle is not always to the strong, or the race to the swift, and whatever works, works. It is a path through a complex environment selected ad hoc by relative success.

    The point I am making is that if a large CC, as well as increasing black hole, caused the universe to be unviable in other ways, then Vilenkin's argument would be moot. And this is not just a counsel of desperation, for plenty of examples in biological evolution show that overconcentration on one benefit is a bad strategy.
     
  6. Oct 5, 2006 #5
    Correct concept - but EM tori rather than black holes

    Lee Smolin has an interesting concept which Alexander Vilenkin attempts to refute.

    There does appear to be an alternative interpretation of this concept - formation of EM tori - rather than black holes per se.

    Torus star formation from rotating discs is discussed in Nature 28 SEP 2006 ‘Infall of gas as the formation mechanism of stars up to 20 times more massive than the Sun’ by Maria T. Beltrán, Riccardo Cesaroni, Claudio Codella, Leonardo Testi, Ray S. Furuya and Luca Olmi in the editor’s summary. doi:10.1038/nature05074
    http://www.nature.com/nature/journal/v443/n7110/edsumm/e060928-06.html

    Artistic illustration at NRAO ‘Astronomers Gain Important Insight on How Massive Stars Form’
    http://www.nrao.edu/pr/2006/starflow/

    Certainly the magnetospheres of many planets and smaller stars are electromagnetic tori.

    Perhaps the galactic centers [black holes] of spiral galaxies are also electromagnetic tori.
     
  7. Oct 5, 2006 #6

    Chronos

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    What SA said [and more eloquently]. Vilenkin's refutation is too simplistic for my taste. It does not appear to consider potential hidden interactions. Sounds like

    'If 1 pill make me feel better, 100 should cure me.'
     
  8. Oct 6, 2006 #7

    marcus

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    I was laughing out loud at your analogy about the pills:biggrin:

    AFAICS Vilenkin did not refute the CNS conjecture as Smolin has described and discussed it. Instead, it looks like Vilenkin modified the conjecture so that it is about a presumed kind of Bh which (without a verified theory of QG) we dont know exists----Bh formed by "quantum fluctuation".

    so it is not a refutation so much as an interesting speculation off in a different direction.

    the CNS Conjecture is essentially a challenge to find a change in one or more constants which would steadily increase abundance of stars collapsed to black holes. It is a conjecture that our set of constants is locally OPTIMIZED for stellar-collapse-to-hole.

    Nevermind why we could be at a local optimum. The evolution picture is a SEPARATE ISSUE and all that goes with it. There is a factual question to be decided. The question is whether or not the constants are at a local max for stellar black hole abundance.

    If they ARE at local max, then we can tell that they are, because then NO WAY YOU VARY THEM WOULD augment stellar-collapse-to-hole. On the other hand if the constants are NOT at local max, it should be straightforward to prove it by finding some way of varying them that promotes holes. So this is a question that can be settled yes or no.

    Vilenkin does not manage to settle it because he goes off on a tangent and talks about the abundance of quantum fluctuation black holes. these may or may not exist and if they were to exist they might or might not have relevance to the evolution of the fundamental physical constants which are embodied in matter.

    But at least now the Old Guard is attempting to dispose of CNS, and Vilenkin goes into contortions to do this. It is interesting that he has to go to such lengths. Maybe there is no simple easy way to refute CNS! And it is also interesting that now Smolin or someone will have to DEFINE MORE PRECISELY WHAT THE ABUNDANCE IS.

    do we put a finite time cut-off and say the # of BH formed by stellar collapse within the first X billion years, or do some other thing to avoid infinities and make sure the concepts like abundance are well defined?
    or do it "per unit volume", or what?
    now that more people are interested it should be possible to make the terms of the CNS conjecture more precise.
     
    Last edited: Oct 6, 2006
  9. Oct 17, 2006 #8
    That is his thesis, and it does not misunderstand evolution. Analogies between CNS and biological evolution (or Alife simulations) are dangerous, because biological evolution has been going on for only a finite time, while CNS is (as far as I know) supposed to go on forever. As long as the probability of jumping out of any local maximum isn't literally zero, eventually it will happen, and eventually almost all universes will have their parameters near the global fitness maximum, so that's what CNS implies. Given an infinite number of tries, even 1 in 10^10^(...) events happen.

    Well, what do you mean by "unviable"? In the CNS model, black hole production is the same as fitness. Overconcentrating on fitness itself is (pretty much by definition) not a bad strategy. Eventually, almost all universes will be optimized for black hole production and nothing else. So unless you're saying that having a larger CC does not give you more black holes, I don't see what your point is.
     
  10. Oct 17, 2006 #9

    turbo

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    Do I mis-read Vilenkin here? He seems to be claiming that given a high enough CC, stars capable of gravitational collapse to BHs will arise from the vacuum as the result of quantum fluctuations.

    It is by now non-controversial that virtual-particle pairs arise and annihilate within the time allowed by the HUP. Additionally, we should expect that some portion of these virtual particles are promoted to real (persistent) status through an infusion of energy (Hawking's BH evaporation model is one such possibility), but whole stars? Is there any school of thought supporting such an idea?
     
  11. Oct 17, 2006 #10
    I'd guess that if single particles can pop out of the vacuum, then if by some preposterous coincidence it happens to a lot of particles at the same time, you suddenly have a star popping out of the vacuum. It seems like another one of those hugely improbable things that will happen if you try infinitely often.
     
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