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If observing the universe affects its duration ? (recent Krauss Dent paper)

  1. Nov 23, 2007 #1

    marcus

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    Highly speculative recent paper by Lawrence Krauss and James Dent.
    Can't help suspecting there is some logical flaw or unjustified assumption.
    In any case the paper is short (only 4 pages) and contains several striking speculative ideas, so some may want to check it out if only from curiosity.

    http://arxiv.org/abs/0711.1821
    The Late Time Behavior of False Vacuum Decay: Possible Implications for Cosmology and Metastable Inflating States
    Lawrence M. Krauss (1,2), James Dent (2) ((1) Case Western Reserve University, (2) Vanderbilt University))
    4 pages, submitted to PRL
    (Submitted on 12 Nov 2007)

    "We describe here how the late time behavior of the decaying states, which is predicted to deviate from an exponential form, while normally of insignificant consequence, may have important cosmological implications in the case of false vacuum decay. It may increase the likelihood of eternal inflation, and may help explain the likelihood of observing a small vacuum energy at late times, as well as arguing against decay into a large negative energy (anti-de Sitter space), vacuum state as has been motivated by some string theory considerations. Several interesting open questions are raised, including whether observing the cosmological configuration of our universe may ultimately alter its mean lifetime."

    Thanks to Peter Woit for noticing this
    http://www.math.columbia.edu/~woit/wordpress/?p=621

    The senior author, Krauss, is a prominent and respected cosmologist (as well as a popular author). I don't recall ever seeing in his professional papers anything that seemed quite so apt to provoke controversy as this.
     
    Last edited: Nov 23, 2007
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  3. Nov 23, 2007 #2

    turbo

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    According to news reports, they have an article in the upcoming New Scientist claiming that we may have hastened the end of the universe by making observations of type Ia SNae the led to the inference of a small positive cosmological constant. Unless their article is being misrepresented or misunderstood, this is some serious disconnect. I can accept the quantum weirdness that says that observing a sub-atomic particle necessarily affects its state, but this? The news report just cannot be right.

    http://www.news.com.au/adelaidenow/story/0,22606,22801758-5005962,00.html

    It will be interesting to see what the article really claims, unfiltered through the popular press.
     
  4. Nov 23, 2007 #3

    Wallace

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    Already being discussed here including posts from the author.
     
  5. Nov 23, 2007 #4

    Chris Hillman

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    Request clarification

    Hang on, are you saying they are themselves writing an article for NS :yuck:, or is their speculation at the end of the cited eprint being written about, no doubt with the maximum of hysteria, by an NS "reporter"?
     
  6. Nov 23, 2007 #5

    turbo

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    More likely. The reporters grab the sensational stuff. Grab Wallace's link for comments by Krauss. It's still REALLY speculative to posit that observing photons from a supernova and inferring the existence of a cosmological constant can have a deleterious effect on the false vacuum from which such cc might arise.
     
  7. Nov 23, 2007 #6

    Chris Hillman

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    Yes, I'm following the other thread too. My understanding is that NS has announced (probably in one of their infamous "press releases"--- talk about involving yourself in the story, on in this case creating the "story"!) a forthcoming NS article by one of the their "reporters", not an NS article by Krauss and Dent.
     
    Last edited: Nov 23, 2007
  8. Nov 23, 2007 #7
    i dont think so either on a minute scale yes but on a universal scale classical physics apply
     
  9. Nov 23, 2007 #8

    turbo

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    Really. If we had the ability to observe all the virtual particles of the false vacuum instantaneously (we don't and never will), we would still have to posit some kind FTL communication to make the claim that we have constrained the state of all those evanescent virtual particles simultaneously. Sakharov felt that experimentation in the field of the false vacuum should be severely limited. I sincerely believe that we are not alone in this universe and that we have no special universal leverage with our observations, and the fact that the universe exists is definitive proof that no other race has such leverage either. The universe is robust against our observations - our sphere of influence is appropriately modest.
     
  10. Nov 23, 2007 #9

    marcus

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    I agree with the generally skeptical tone of the comments and just have two things to say.

    1. I didn't realize when I posted that someone else had already initiated discussion. There is another thread about this, as Wallace pointed out a few posts back, which seems to focus more on the popular media reaction (judging by links in the O.P.)

    2. I respect Larry Krauss in general very much both as a scientist and as a writer.
    One of his papers this year was called something like the Static Universe and the End of Cosmology----about what the late universe will look like according to the accepted LambdaCDM model. Beautiful and eye-opening paper.

    Nevertheless a couple of sentences in the conclusion in the present paper totally do not make sense to me.

    Krauss contributed a couple of brief posts to the other thread and Wallace rebutted.

    ==================

    UPDATE
    Krauss has revised the paper on arxiv. Hopefully this will make it less provocative and help damp the media reaction.

    Here is the new abstract summary, so you can compare it with what is in the O.P.
    ==quote Krauss Dent abstract==
    We describe here how the late time behavior of the decaying states, which is predicted to deviate from an exponential form, while normally of insignificant consequence, may have important cosmological implications in the case of false vacuum decay. It may increase the likelihood of eternal inflation, and may help explain the likelihood of observing a small vacuum energy at late times, as well as arguing against decay into a large negative energy (anti-de Sitter space), vacuum state as has been motivated by some string theory considerations. Several interesting open questions are raised, including whether observing the cosmological configuration of a metastable universe can constrain its inferred lifetime.
    ==endquote==

    The last couple of sentences in the main body of the article are also toned down or perhaps tastefully obfuscated :

    ==quote==
    ...ensured, by measuring the existence dark energy in our own universe, that the quantum mechanical configuration
    of our own universe is such that late time decay is not relevant? Put another way, what can internal observations of the state of a metastable universe say about its longevity?
    ==endquote==

    there is still some sensational content but you have to stretch a little and dig more to get it.

    KRAUSS THINKS HE HAS REMOVED ANY SUGGESTION OF CAUSALITY by changing the last two sentences, he says on Woit's blog
    "... In any case, the last two sentences of the paper have been revised so that it should be clear to the press that causality will not be implied."
    http://www.math.columbia.edu/~woit/wordpress/?p=621#comment-31045

    In other words there is now supposed to be no suggestion that our observing the CC can have caused anything. In my humble, he is fooling himself and he will still have to revise further, before the paper is published, or perhaps eliminate the last two sentences.
     
    Last edited: Nov 24, 2007
  11. Nov 24, 2007 #10

    marcus

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    After I wrote the above, about their changing the paper, Larry Krauss happened to show up and kindly pointed that out in the other thread:
    So that's apparently settled now. The paper is NOT supposed to give people the idea that our observing the cosmo constant etc has any effect on universe future rates of expansion.

    Hope they can get the word out so as to correct any earlier misinterpretation.
     
  12. Nov 25, 2007 #11

    George Jones

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    [EDIT]Controversy is not necessarily a bad thing, and, in the right context, can be quite a good thing, as it generates much discussion. If no one pushes the envelope, science doesn't advance very far.[/EDIT

    Krauss is also a co-author of the Phys. Rev. D accepted

    http://www.arxiv.org/abs/gr-qc/0609024

    which generated a bit of controversy controversy a few months ago.

    The main (and controversial) point of the paper: *no* observer (hovering, freely falling, blasting away with a rocket *towards* the surface of the collapsing object, etc.) experiences an event horizon because there is no event horizon to experience.

    From the paper: “Instead it may happen that the true event horizon never forms in a gravitational collapse ... The infalling observer never crosses an event horizon, not because it takes an infinite time, but because there is no event horizon to cross. As the infalling observer gets closer to the collapsing wall, the wall shrinks due to radiation back-reaction, evaporating before an event horizon can form. The evaporation appears mysterious to the infalling observer since his detectors don’t register any emission from the collapsing wall Yet he reconciles the absence of the evaporation as being due to a limitation of the frequency range of his detectors. Both he and the asymptotic observer would then agree that the spacetime diagram for an evaporating black hole is as shown in Fig. 9. In this picture a global event horizon and singularity never form. A trapped surface (from within which light cannot es cape) may exist temporarily, but after all of the mass is radiated, the trapped surface disappears and light gets released to infinity.”
     
    Last edited: Nov 25, 2007
  13. Nov 25, 2007 #12

    Chronos

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    I really respect Dr. Krauss's responsiveness to our criticisms. Isn't that the kind of reaction a well regarded science forum should provoke?
     
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