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Baby Universes in String Theory

  1. Apr 27, 2005 #1

    marcus

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    just out, in case anyone is interested
    http://arxiv.org/abs/hep-th/0504221
    Baby Universes in String Theory
    Robbert Dijkgraaf, Rajesh Gopakumar, Hirosi Ooguri, Cumrun Vafa
    39 pages, 7 figures

    "We argue that the holographic description of four-dimensional BPS black holes naturally includes multi-center solutions. This suggests that the holographic dual to the gauge theory is not a single AdS_2 times S^2 but a coherent ensemble of them. We verify this in a particular class of examples, where the two-dimensional Yang-Mills theory gives a holographic description of the black holes obtained by branes wrapping Calabi-Yau cycles. Using the free fermionic formulation, we show that O(e^{-N}) non-perturbative effects entangle the two Fermi surfaces. In an Euclidean description, the wave-function of the multi-center black holes gets mapped to the Hartle-Hawking wave-function of baby universes. This provides a concrete realization, within string theory, of effects that can be interpreted as the creation of baby universes. We find that, at least in the case we study, the baby universes do not lead to a loss of quantum coherence, in accord with general arguments."

    if you have any interest in Smolin's Cosmic Natural Selection conjecture you might like to look at Figure 7 on page 29 of the Vafa-et-al paper
    just for the stimulation of superficial resemblance
     
    Last edited: Apr 27, 2005
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  3. Apr 27, 2005 #2

    selfAdjoint

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    "More powerful than an army with banners, is an idea whose time has come"
     
  4. Apr 27, 2005 #3

    marcus

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    LOL, I mean that. laughing out loud

    (and just to elucidate the slightly tongue in cheek tone of your post, we both know damn well that it may be a wrong idea!)

    that is not enough exclamation marks, stringbabies and CNS may both be a wrong idea!!!!

    that said the idea does seem to be developing a bit of buzz
     
  5. Apr 28, 2005 #4

    selfAdjoint

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    Right or wrong, it's a HOT idea! As such there will be an attraction for bright young researchers. If the early tries pan out, look for a feeding frenzy as everybody wants to get credit for being early onto the new new thing. Like last year with DSR.

    Evolution (random gerational variation and natural selection) is still the only known mechanism for building complexity and "tuning" without some genuflection to ID. So if somebody can make a plausible case that it can take place in one context, lots of people are going to ask themselves whether it would work in their neck of the woods.
     
  6. Apr 30, 2005 #5

    marcus

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    Today Lubos commented on the article that is the topic of this thread.

    http://motls.blogspot.com/2005/04/stringy-baby-universes.html

    In the preceding segment of today's blog, Lubos had just said:
    "Unfortunately, I currently do not enjoy the freedom to tell you what I think about these things."

    One does not know how much pressure (if any) Lubos is actually experiencing and about what----i.e. how broad the category "these things" actually is. It may only refer to the judicial appointment filibuster or it may involve something more general, like style.

    Lubos signs himself "lumo (leashed)" after his discussion of the
    "Stringy Baby Universes" paper of DOGV (Dijkgraaf, Gopakumar, Ooguri, and Vafa).

    It seems clear that he is not enthused about DOGV interpreting their results as providing for "Baby Universes" in a stringy context. However IIRC Vafa is the Harvard physics department chairman and one of the most prominent and energetic leaders in the string theorizing field. I believe Lubos likes to be in agreement with Vafa, he often sounds like that, and I do not know to what extent he would want to express displeasure and skepticism about a paper by Vafa.

    In any case Lubos can't expect to sign a lukewarm review of an article by his department chair and one of the most powerful people in string theory with a signature like "lumo (leashed)" without exciting some curiosity
     
    Last edited: Apr 30, 2005
  7. Apr 30, 2005 #6

    wolram

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    One has to read the quisquiliae to find the truth.
     
  8. Apr 30, 2005 #7

    marcus

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    It seems to me that we dont know for sure that the BH-to-BB connection will work out in EITHER LQG or string/M.

    It appears to have been made with some simplifying assumptions by Modesto and by Husain and Winkler, using a version of QG that is not strictly speaking LQG.

    But Bojowald (and Ashtekar in one case) and others using more usual LQG methods have not unequivocally established it. To my mind it could go either way.

    1. it might be that both LQG and string are wrong and will fail as theories

    2. even if one of them turns out to be an adequate theory of gravity, i.e. spacetime geometry, and gives an adequate description of black holes then it might be that the successful theory DOES NOT PREDICT a connection like this that would join BH to BB and allow "baby universes" to form

    the term "baby universes" bugs me---I am not sure everybody who uses that term means the same thing. I mean a BH-to-BB bounce as found to occur in the theoretical model used by Modesto and Husain-Winkler.

    Not yet found by Bojowald. In fact assumed not to occur in a recent paper by Bojowald and Ashtekar. they said: in this paper, we assume that kind of bounce does not happen, which is one possible assumption, it might but we are studying the case where it doesnt.

    it seems that this issue is still very much undecided both in string/M and in Loop.
     
  9. Apr 30, 2005 #8

    marcus

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    my dictionary says that a quisquilia is "a trifle, a bagatelle"

    and it even sounds like a suggestive murmer or whisper

    exquisitely choice of word, even if the intent was satirical
     
    Last edited: Apr 30, 2005
  10. Apr 30, 2005 #9

    wolram

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    String and LQG are still in the nursery, i doubt if string will ever reach
    adulthood, " thats only my take on it", until we have some data to go on
    all this positing is useless.
    CNS is a good theory that is falsifiable to some extent, but we need to learn
    almost all of cosmology to do so.
     
  11. Apr 30, 2005 #10

    marcus

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    you are right. an awful lot has to be learned before the effect of a small variation of the parameters can be understood in terms of BH abundance
     
  12. Apr 30, 2005 #11

    wolram

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    The spirit of man isinexpugnabilis we must go forward, "somehow" :smile:
     
  13. Apr 30, 2005 #12

    marcus

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    Hah! I caught that before Peter Woit noted it!

    He just now posted
    http://www.math.columbia.edu/~woit/blog/archives/000189.html

    An (ex-physicist) blogger named Capitalistimperialistpig said
    http://capitalistimperialistpig.blogspot.com/2005/04/lumo-leashed.html

    "My dark suspicion is that he might have gotten caught in a PC violation in the Summers Affair, forcing him to do a T reversal to save his Lorentz invariant m ass."

    to which, this morning, the Motly one replied

    "Unfortunately your intuition is perfectly correct, but I am not sure whether your imagination is big enough to imagine the scale."
    Luboš Motl 04.30.05 - 7:55 am
     
    Last edited: Apr 30, 2005
  14. Jun 20, 2005 #13

    marcus

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    Robbert Dijkgraaf will give one of the two public lectures at the big annual string conference Strings 05
    July 11-16 Toronto
    http://www.fields.utoronto.ca/programs/scientific/04-05/string-theory/strings2005/program.html

    and the title of Dijkgraaf public lecture will be "String theory, black holes, and the end of space and time."

    this looks like it might relate closely to the "Baby Universes" paper
    which suggests the possibility that time can fork or branch in string theory (as it has already been conjectured to do in LQG by Smolin and others).

    one cant consider it a proven consequence of some version of string theory or of LQG either, just a possible feature of either theory
    (also this is just a guess about the subject matter of Dijkgraaf's talk)

    but the rough idea is that the universe can continue out from the pit of a black hole to produce a new, expanding tract of spacetime---and maybe like Dijkgraaf says there can even be multiple centers so that not just one but several new universes escape out the black hole back door

    the key point is that time forks----it isnt the old single-track time we are used to because the unverse re-expanding from the black hole pit has its OWN FUTURE which is different from our future in our branch of the universe that stays out of the black hole and keeps from falling in.

    if you fall in, then the energy or particles comprising you have one future, and if you dont fall in then that energy or particles has another different future. maybe i am wrong but I think that means the end of time as we know it, the old familiar concept of time doesnt branch

    well this is just a guess, not to take seriously, and we will probably find out soon enough what Dijkgraaf has in mind about "the end of space and time" when he gives his public lecture 16 July. they will put the audio online, or somebody will report.
     
    Last edited: Jun 20, 2005
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