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A scientific multiverse theory

  1. Aug 2, 2004 #1

    marcus

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    A theory is scientific if it bets its life on at least one prediction that it makes about the outcome of a doable experiment

    If a theory is part of science then there's a possibility it'll get shot down by an empirical observation---by some measurement----the theory makes predictions of so far unknown results that are that clear and unequivocal.

    Smolin has come out with a Multiverse theory which can be shot down if anyone finds a neutron star of 1.6 solar mass or heavier.

    Smolin Multiverse is not really part of LQG it just uses LQG-brand plumbing.
    It happens to use LQG-brand fittings to connect the end of a black hole to the beginning of a universe.

    But quantum gravity in general or LQG in particular does not need Smolin Multi to resolve some crisis. As far as QG goes it is fine if Smolin Multi gets shot down! We still have the good plumbing. And probably some other reason will turn up telling why 1/137 is 1/137 (which is for particle physicists to worry about anyway)

    Smolin Multi is a falsifiable theory that offers a way to explain parameters in the standard model (particles) and the standard model(cosmology).
    It should explain why 1/137 and why
    planck/proton mass is 13E18
    and why cosmo.constant is E-123
    (Smolin says "the dimensionless parameters of the standard models of physics and cosmology", these are examples). And if Multi fails and dies on the launchpad, well there will be other explanations of those parameters.

    Smolin Multi says that sets of basic constants become very common if they promote the formation of black holes. this is testable.
    Maybe there is one of our standard model parameters which is not adjusted to promote holes. OK find it.

    So according to Multi if there actually is an ensemble of universes then those with hole-promoting ("holific"?) parameters are very common---the overwhelmingly most common are universes presumably like ours, in that they promote holes. The inference is that our parameters are not especially rare!

    Conscious life is accidental to the theory. I suppose it could play a role in some variant theory but it doesnt----Multi is simple and doesnt need to consider that angle. In Multi what drives evolution is holes and only holes.
    The conclusion is that what we've got is apt to be very common.

    there are other Multiverse stories floating around in which our type of universe is very rare. there is an ensemble of a huge number of universes which are unfriendly to life or otherwise inconvenient. these are not predictive AFAIK because the premise cannot be shot down by some future empirical observation. those stories do not predict anything (we live in a rare exceptional case and are excused from explaining why it is like this) so they are cop-outs.

    At least one such non-scientific Multiverse story seems to have been invented in response to the string theory Kachru crisis of too many vacuums.
    But this doesnt matter. the main thing is we now have a Multiverse theory which (whether its wrong or right) predicts something definite for checking where we dont yet know the outcome.

    http://arxiv.org/hep-th/0407213
    Smolin
    Scientific alternatives to the anthropic principle
     
    Last edited: Aug 2, 2004
  2. jcsd
  3. Aug 2, 2004 #2
    So, what Smolin is saying is that at a black holes singularity, it will tear the facric in spacetime? Then a flop transition or something occurs and a new universe is born, or what?

    Paden Roder
     
  4. Aug 2, 2004 #3

    marcus

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    about the plumbing that connects what used to be a singularity in BH to what used to be a singularity in BB there are some papers by other people.
    it is essentially off the shelf connectors

    getting rid of the BH singularity:
    Leonardo Modesto
    http://arxiv.org/gr-qc/0407097

    getting rid of the BB singularity:
    Martin Bojowald
    http://arxiv.org/gr-qc/0102069

    Bojo result has been extended and confirmed many times by many people in the years since 2001 and a recent paper is
    Date and Hossain
    http://arxiv.org/gr-qc/0407074

    Bojo is the king of removing singularities
    and the recent surprise is that although he was working
    on eliminating the BH singularity and had not yet
    posted, yet suddenly a new-comer Modesto (apparently a postdoc working
    for Rovelli in Marseille) posted.

    I think it is a safe bet Bojowald will present his removal of the BH
    singularity and then (for me) that will be somewhat more trustworthy
    than the work of Modesto, whom I never heard of till now.
    ----------------------------

    Smolin's paper is more than just connecting the pit of a hole to the beginning of a universe.
    (that part is the plumbing connectors bit)

    what Smolin presents is a theory of how fundamental physical constants evolve
    A. if every black hole terminates in a bounce from which buds a new universe
    B. and if the constants of the laws of physics only change slightly as they go thru the hole

    then it will lead to an overwhelming predominance of sets of constants which are good for making holes---a typical U will be one that makes a lot of holes.

    so first of all it has to have enough gravity to pull stars together, and enough chemistry to radiate heat of condensation away, and enough lifetime to let stars and galaxies form, before the universe itself collapses, and when neutron stars form (as in a supernova) there has to be some limit to how big they can be before they too collapse and make a BH, and so on-----physical constants that influence these things (like a stable carbon atom is a Good Thing for radiating away heat when stars condense) will be affected by evolution and move towards high-fitness configurations.

    So you can see ProdQ that Smolin is talking more about what makes the fundamental physical constants what they are. It is not just the LQG joint between a hole and a universe. he is making a theory with explanatory power which he neither believes nor disbelieves but challenges us to test.
    Can you prove this wrong? Can you show the constants do not evolve so as to favor blackhole formation?

    the aim, I think, is to exhibit a testable Multiverse theory. One that predicts something instead of just being a nice daydream
     
  5. Aug 2, 2004 #4
    (edit: never mind, I've already said all this in the other thread)
     
  6. Aug 2, 2004 #5

    Chronos

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    Interesting. Since the electron degeneracy limit is thought to be ~1.44 solar masses and the neutron degeneracy limit is thought to be ~ 3 solar masses. So the obvious question is what happens between 1.6 and 3 solar masses? [Maybe I just need to read Smolin's paper :)].
     
  7. Aug 2, 2004 #6

    jeff

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    And scientific research programs have the goal of producing scientific theories.
     
  8. Aug 2, 2004 #7

    marcus

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    I agree with jeff about this.
    I imagine that what those who fund and direct research programs would
    like to see, in some instances, is steady progress towards the goal of
    a testable predictive theory----it wouldnt be reasonable to demand of a young theory still under construction that it be already at that point. (But I mustn't pretend to guess how NAS committee-wizards think, there could be a lot of politics to it.)
     
  9. Aug 2, 2004 #8

    marcus

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    chronos, I expect you have looked at pages 33-34 of smolin's paper
    section 6.3 "why a single heavy pulsar would refute [the theory]"

    It is a short passage (much of which i cant follow) that relies on work by Hans Bethe and George Brown. Bethe and Brown calculated a dependency between the strange quark mass mu and the upper limit on neutron star mass. If the real mu is below a critical value which they called mu-crit then there is a low upper bound on neutron star mass----Bethe and Brown estimated it to be 1.5 solar.

    there is nothing special about the number 1.6, it is just something clearly bigger than the bethe and brown 1.5. Instead of 1.6 let us be generous and say 2.

    If one would find a neutron star of 2 solar mass, then one would reason that the strange quark mass mu is greater than the mu-crit that Bethe-Brown calculated.

    then one would say "if nature had made mu smaller then some of these more massive neutron stars would have collapsed to form holes! So nature is a slacker! She is not making as many black holes as she could be!"
    And this would shoot down Smolin's conjecture that we live in a Multiverse which has evolved to produce lots of holes. It would make it very improbable that this is the case.

    Now so far my grasp of this is only partial and I have to look at the Bethe Brown papers---since Smolin is building on their work---and make sure I have it right.

    these papers are:
    "Kaon condensation in dense matter"
    "Observational constraints on the maximum neutron star mass"

    plus 2 papers from 1994 in Astro. J.
    and 1 paper from 1994 in Nucl. Phys. series A.

    I will try to post a link to the "Observational Constraints" paper since that will have references to the others.
     
  10. Aug 2, 2004 #9

    jeff

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    Precisely my friend.
     
  11. Aug 3, 2004 #10
    Thanks marcus.

    Paden Roder
     
  12. Sep 22, 2004 #11

    Chronos

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  13. Sep 23, 2004 #12

    marcus

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    bad news for Smolin's CNS (cosmic natural selection) theory

    maybe not conclusive yet, their lower limit 1.88 solar might not shoot it down but their upper limit 2.27 +/- 0.17 solar masses looks like it would refute the theory if it were confirmed that the neutron star was in fact that massive.

    thanks for finding this! Now I must re-read Smolin's artilce to make sure that I have not made an error.

    here is the online preprint of that article
    http://arxiv.org/abs/astro-ph/0301243
     
    Last edited: Sep 23, 2004
  14. Sep 23, 2004 #13

    Chronos

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    My bad, I am such a maverick. That prediction really bothered me and I could not help commenting about it. I admit to being a die hard skeptic. I wasn't even looking for that information, just stumbled upon it.
     
    Last edited: Sep 24, 2004
  15. Sep 23, 2004 #14
    I looked at the paper and saw it was dated back to January 2003 but in the Edge discussion (posted after Jan. 2003) Smolin still defends his CNS scenario, so I don't believe it has been falsified.
     
  16. Sep 23, 2004 #15

    marcus

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    On the contrary, your good

    scientific theories are meant to be shot down.

    Maybe this observation does not absolutely conclusively shoot down CNS.
    But it seriously crowds it IMHO.

    My guess is that Smolin did not know about this observation, or he would have mentioned it (challenged it, or pointed out that it was not conclusive because 1.88 solar masses is still a possible interpretation.)

    It is interesting to notice what Smolin gives as his reason for presenting CNS theory in this paper. He uses it to show that one can have a multiverse theory which makes testable predictions and does not appeal to the Anthropic Principle.

    Smolin's quantum gravity ideas do not depend on CNS. It is an intriguing idea but disproving CNS does not disprove LQG.

    Maybe one of us should write Smolin email about this 2003 observation.
     
  17. Sep 23, 2004 #16

    marcus

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    I can only assume no one told him about this observation of a rather massive neutron star. Or does he require TWO observations of a neutron star that is too massive for his theory before he cries "uncle"?
    I dont know what we should do about it, if anything. Write Smolin? He should at least insert a footnote in his essay to be published ("this theory has subsequently been shot down, see, I told you it was falsifiable!")

    I look on this with some degree of equanimity. CNS is a nifty theory but there will be other explanations offered for why the constants have the values we see and at least some of the theories will be testable, like CNS,
    by making predictions.

    maybe Smolin himself will come up with another candidate.

    I suspect the values of some of the basic physical constants really are explainable by a predictive theory---and applaud the ambition of anyone audacious enough to propose one.
     
  18. Sep 23, 2004 #17
    I have always suspected that Smolin WANTS to have the CNS through BH theory shot down- just to proove his point that falsifiable multiverse theories are possible and that it isn't necessary to rest on the Anthropic principle-
     
  19. Sep 23, 2004 #18

    marcus

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    :smile:
    that thought has crossed my mind too
    (maybe in 1995 he proposed it seriously and hopefully but
    now in 2004 is using it in just the way you indicate)
     
  20. Sep 23, 2004 #19

    Tsu

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    Well... so who's going to email him????!!!!!! Let's get this goin! :smile:
     
  21. Sep 24, 2004 #20

    marcus

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    commendable impatience Tsunami, he has been notified
    (someone I know just emailed him)

    If there is any credit for Chronos noticing this he should write Smolin
    himself. my friend did not mention PF or the source of the information, just sent the link to the paper.
     
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