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Any better reasons than this one for not believing in the landscape?

  1. Nov 20, 2005 #1
    Hi all,

    Time to start my first thread, so here goes.

    The difficulty I have with the landscape is this: How could the solution that seems to describe our universe be the ugliest possible one in a theory whose structure is otherwise supposed to be so deep, beautiful, elegant or whatever?

    Does anyone have better reasons for rejecting the landscape?

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  3. Nov 20, 2005 #2

    marcus

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    Hi josh1,

    your "sig" is kind of a translation of an earlier poster named Jeff's sig. You might be interested to look back at some of his posts! since you you share the same "sig" in a certain sense---have that characteristic in common.
    Jeff sig was a shorter "Keep it to the physics" which I suppose was good advice quoted from some PF higher-up. I believe he kept this on his posts as a reminder to himself and everybody to be friendly to people and quarrel only with ideas. (or so I think it meant.)

    You might find it really interesting to search back to posts of a possible chance resemblance if not actual kindred spirit. BTW Jeff is author of the sticky you see in this String&QG forum about Useful Literature.
     
  4. Nov 20, 2005 #3
    1+2=1 or 2 or 3 or 4 or 5 or 6 or 7 or.... which of course might be true, but is no answer.
     
  5. Nov 20, 2005 #4

    marcus

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    Hi josh1 (I almost said jeff :smile: he used to post favorable to the landscape and the anthropic on SPR, if I remember correctly)

    I think my attitude may be atypical, but you ask it as open question so anybody can answer. I don't belong to a school of thought. I find that the string framework simply does not INTEREST me
    because it does not start by providing a model of quantum dynamic spacetime

    so accepting or rejecting the string "landscape" never comes up as a big issue.

    I don't find the string approach has much PROMISE or verisimilitude as a QG approach-----your question seems to have some unspoken premise that it is promising, so one needs reasons to reject this or that version.

    So I will be glad to try to explain, if you wish, why the whole framework has little promise or interest compared to other QG for me.
     
  6. Nov 20, 2005 #5
    Maybe I'm being stupid, but I don't get it.

    Good, neither do I.

    No problem. In fact I’ve noticed the way you bring to the attention of other member’s papers and other things related to LQG etc. The reason I’m on no one’s bandwagon is because I don’t see how any of the current theories can resolve the problem that’s most interesting to me, which is of understanding how the universe collapsed into the classical one we see today. This is one of the reasons why I tend to want to discuss the problems more than the successes of any given theory. But I’m not going to force my own sensibilities in this regard down anyone’s throat.

    You can if you want, but given what you said, the fact that string theory has nothing to say about quantum dynamic spacetime is reason enough.
     
  7. Nov 20, 2005 #6

    marcus

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    Your attitude intrigues me josh1.
    I want to ask you to describe the problems of Loll CDT.
    If you wish, you could do so briefly in this thread. But if you would rather keep this thread focused on the Landscape issue, then I would welcome if you would start another thread about the problems you see with CDT.

    It seems to me that your big interest, as you say, is how the universe collapsed into the classical one we see today and this is precisely what is addressed Loll's papers "emergence of a 4D spacetime" and "reconstructing the universe". the papers are far from providing a complete answer but they seem to make progress in addressing your number one issue

    also your comment on the Hal Finkel stuff in Smolin's talk would interest me----where they start with a random network and apply evolutionary moves to it and it gradually smooths out and looks more classical except for some small amount of long-distance links which then he proposes to identify the ends of non-local links with particles of matter

    both the Loll CDT and the Hal Finkel simulations are dealing with ADMITTEDLY SPECULATIVE pictures of the genesis of classical spacetime by a series of moves in a combinatorial scheme (a network, an assemblage of building blocks) so they seem right down your alley. Would appreciate your comment either here or in separately created threads :smile:
     
  8. Nov 20, 2005 #7
    Hi Josh - why is it ugly?

    There seem two alternative views on the landscape.

    1) The first is that it is a set of crisp probabilities. That is, every possible solution actually has existence and we happen anthropically to be in one outcome in which existence can be reported.

    2) The second would be that the landscape represents a realm of vague potential - a general urge to do something dimensionally speaking. There are again many potential outcomes. But only one is the minima, the lowest self-organsing state.

    3) In between these two extremes, perhaps it is possible to have a small number of actual minima resulting from the dissipation of the vague potential.

    I would say 1 and 3 were kind of ugly. But 2 seems very attractive to me. I find anything that demands a crisp beginning state and sudden creation events (or alternatively, eternal existence) to be ugly. But a solution that combines the dichotomy of the ultimately vague and the ultimately crisp seems to include all possibility in a smooth organic way.

    Cheers - John McCrone.
     
  9. Nov 21, 2005 #8
    so could another way of looking at the landscape be...

    ...instead of the possible number of vacua present at any one time in a multiverse scenario...

    the number of possible permutations/variations of a string vibrating in a multi dimensional scenario at any one time ???
     
  10. Nov 21, 2005 #9
    Is the vacuum of our universe simply the result of how some symmetry involved with the landscape happen to break? If so, then what symmetry is it that broke in our favor? Thanks.
     
  11. Nov 21, 2005 #10

    selfAdjoint

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    According to string theory, yes.

    Precisely what they can't answer. Hence "The Landscape Problem".
     
  12. Nov 21, 2005 #11
    anybody want to give this a simple yes/no and a why/not would be good too if you can manage...

    ... ta :wink:
     
  13. Nov 21, 2005 #12

    CarlB

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    Okay, here's one. The landscape presumes that the universe can occupy any of a number of equally possible vacuums. But the quantum mechanical concept of vacuum is not well established in physics. Only one vacuum has ever been observed.

    Julian Schwinger won the Nobel prize for discovering QED in the 40s but soon came to the conclusion that the vacuum was not physical. One of the better arguments for the vacuum being real was the Casimir effect which is usually calculated using the vacuum energy. So went on to derive the Casimir effect without the assumption of the vacuum.

    And if there is no vacuum, then there is no landscape.

    In a certain way, the vacuum amounts to a linearization of quantum mechanics. Without the assumption of a vacuum, the fundamental equations would be quadratic instead of linear. Since linear mathematics is far better developed than nonlinear, our using the linearization of QM amounts to the drunk searching for his wallet underneath the lampost with the most light rather than where he lost it.

    Carl
     
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