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Radical new take on *uni*verse questions by Smolin, could be important

  1. Apr 4, 2013 #1

    marcus

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    Smolin has a new book (Time Reborn) coming out this month. Amazon has a page on it, with advance reviews.

    He gave a talk on the main ideas at Perimeter in February. I was impressed by the depth and cogency. It is a 60 minute talk followed by a lengthy discussion with Rob Myers, Laurent Freidel, Neil Turok and other members of the Perimeter audience. Here's the video:
    http://pirsa.org/13020146/

    The first 35 minutes lays out the main ideas for wide audience and is readily understandable. I think it would well repay anyone's time to listen to it. He presents certain principles (buttressed by quotes from Dirac, Feynman, Wheeler, Peirce) some going back to Leibniz. In the next 25 minutes he presents new work on a spacetime and quantum dynamics based on those principles which he and a collaborator are currently attempting to simulate in toy version on computer. Some advanced background is needed to understand the final 25 minutes of the talk. He constructs one or more actions/Lagrangians based on simplified models under study.

    The enterprise is high risk. As I recall, the most active audience member is Rob Myers, who keeps commenting and asking questions both during the first hour and in the following 20 minute discussion. But Laurent Freidel is pretty active too. The enterprise could clearly fail. However I find it very interesting and having a real potential to change the foundations.

    I'd appreciate comment from anyone who has listened to (at least the first half hour or so of) the talk.
     
    Last edited: Apr 4, 2013
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  3. Apr 4, 2013 #2

    marcus

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    There was a 2011 pirsa video talk by Smolin that could be viewed as a kind of preamble to this talk:
    http://pirsa.org/11100113/

    One nice thing about the pirsa format is you can click on the slides PDF and get stills as a convenient way of reviewing the talk. I will keep the PDF for the February 2013 talk on my desktop for a while, to have as reference.
    http://pirsa.org/13020146/

    ===example, slide 6 of PDF, quote===
    We start with Leibniz:
    Priciple of sufficient reason (PSR): Every question of the form why does the universe have property X rather than Y must have a rational answer.

    Principle of the identity of the indiscernible (PII): Any two events with the same properties are identical.

    Consequences:
    No unreciprocated actions: No non-dynamical background structures. No unalterable, timeless laws somehow acting inside of time.

    Causal completeness: Explain the universe only in terms of itself. No reference to other universes, non-realized ensembles, or other, Platonic, realms.
    ==endquote==
     
    Last edited: Apr 4, 2013
  4. Apr 4, 2013 #3

    marcus

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    I think those 4 principles in post #2 are worth thinking about so I'll put them by themselves.
    No multiverse.
    At least some laws of nature would seem to be emerging and evolving from a temporal process.
    This is a radically distinct viewpoint, although he cites antecedents for it.
    Laws not standing fixed and eternal outside or above nature, but being an evolving part of nature.
    At first sight it seems so radically different that it would HAVE to be wrong!
    But maybe it isn't.

    Then in the next few slides he lays out some QUESTIONS to be addressed:

    ==sample excerpts taken from slides 7 and 8==
    ....
    ....
    Here are two big questions that we lack sufficient reason for:

    Why these laws?

    Why these initial conditions?


    Both appear to have been finely tuned.

    ....
    ....
    Here are two other issues we will address:
    Why does the unverse have a strong arrow of time?

    What causes events?
    ==endquote==
     
  5. Apr 5, 2013 #4

    Chalnoth

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    I would say that the statements about time and timesless laws don't make sense in the context of this work by Albrecht and Iglesias:
    http://arxiv.org/abs/1003.2566

    Basically, you can always re-cast whatever laws you might write down in terms of some laws that are time-invariant.
     
  6. Apr 5, 2013 #5

    marcus

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    How much of Smolin's talk did you watch? I ask because your comment and the paper you cite do not seem to connect at all with what I was saying or with the talk.

    You seem to be using the word "timeless" to describe a law whose statement simply does not involve the time variable.
     
  7. Apr 5, 2013 #6

    Chalnoth

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    I didn't listen to it. I skimmed the PDF. Maybe he's trying to use it in a way completely different from what his slides seem to imply, but it just doesn't make sense to me the way he writes it, though I guess in part that's because I don't at all know what he means by the claim that time is somehow "real".

    In any event, I really do think the most likely description of our universe is one in which there is a single mathematical structure which describes all interactions, and the slides make it seem like that is precisely what he is attempting to argue against.

    I also am incredibly skeptical as to the idea that he lays out that the fundamental laws of physics should be asymmetric in time and coarse-grain to time-symmetric laws with asymmetric initial conditions. That does not strike me as a pursuit that is likely to bear fruit.
     
  8. Apr 5, 2013 #7

    marcus

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    Listening to the first 30 minutes is a really good way, I find, to understand what he's driving at. I'll try to give a secondhand explanation too, but it is no substitute.

    What you say about not "likely to bear fruit" is true about a lot of highly original ideas that people try out. Most do not succeed. I mentioned earlier that this is a "high risk enterprise". Part of why it looks interesting and valuable to pursue. But it has other important merits in its favor as well, I think. This is not just any off-the-wall gambit.:biggrin:

    To paraphrase, to give additional clarification for those who have watched the first 30 minutes or so, I think he's saying that the "block universe" is a fiction. We know that already, just as "continuous trajectory" of a non relativistic particle is a fiction.

    And the idea of unchanging physical laws is a fiction. The idea of block universe being created together with what we think of as the unchanging laws of physics, which are imagined to govern that block universe without themselves suffering alteration by interaction with it, is contrary to the basic (Leibniz) principles he has adopted. He's following out the consequences of a couple of basic assumptions that I quoted earlier.

    So there is some kind of "meta-law" or process (not necessarily representable in equation form) according to which the emergent regularities (which we think of as the laws of physics) evolve. Those regularities are part of the universe and they evolve along with the rest of the universe that they are part of. They only appear to us to be unchanging fixed proportions or formulae.

    This "meta-law" process, vaguely analogous (one could imagine) to the evolution of biological species where the species takes the place of an "event" in the meta-law scheme, defines a kind of TIME. I would picture this as LAYERS of an evolutionary process, you see pictures of that in the slides PDF. This time is not necessarily the coordinate or real-number parameter sort of time you may habitually think of. It could be more like the layers in sedimentary rock, more like geological or bio-evolutionary time. It is the time which is intrinsic to the evolutionary meta-law process itself.

    However later in the talk, after minute 35, he does get into writing Lagrangians and talking about equations of motion (EoM). To do that he has to use a kind of normalization number r, which you could think of as like a cutoff parameter. Each event is required to have r parents and r offspring. A layer of time is complete when each event in it has the expected number of parent and offspring. This seems to be an arbitrary condition to impose, but it gives him traction so that he can move ahead with the computer simulation.

    It means that the Lagrangian treatment of the second half of the talk, and the computer simulations he and collaborator are working on, are exploratory toy model stuff.

    Anyway it's an interesting adventure, and because what we think of as physical laws evolve along with everything else in the universe according to this process of causation, the time intrinsic to this process must be real and fundamental.

    It is not the t ∈ ℝ calculus time pertaining to some imagined eternal law of physics (that sort of time could be subsumed into some static picture as a coordinate) because what we think of as laws of physics are themselves evolving regularities. In response to your comment then, time in Smolin's sense must be real because the process of evolving nature is fundamental and requires time---other stuff are ephemeral patterns of regularity which appear or develop in the process.

    He is trying to explain the existence of what we consider to be the laws of physics, see the slides 6, 7, 8 where among other things he asks "Why these laws?"
     
    Last edited: Apr 5, 2013
  9. Apr 5, 2013 #8

    Chalnoth

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    Maybe I'll take a look when I get home later.

    To me, this particular feature makes it an off-the-wall gambit. He's basically saying that a macro property which isn't at all visible in our currently-known micro laws, but can be understood as a result of particular initial conditions, must actually be a result of even more microscopic laws. It's a strange sort of averaging that causes an effect to disappear only at intermediate scales, but is clearly-visible both at microscopic and global scales.
     
  10. Apr 5, 2013 #9

    marcus

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    Good. Looking forward to your comments.
     
  11. Apr 7, 2013 #10
    Pretty early on in the talk, he said something like "There are no global Killng vector fields on the config/phase space of GR with cosmological boundary conditions". Can anybody clarify what was meant, or provide a reference?
     
  12. Apr 8, 2013 #11
    It may be felt that my thoughts are not worth putting down but watched the first 40 mins, finally someone with thoughts similar to mine regarding time, he's going in the right direction. Be interested to see if he can put things together or loses sight of the basics in complexity of his own making. If he gets it right then string theory RIP.
     
  13. Apr 8, 2013 #12

    Chalnoth

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    It may help to read up on what a Killing vector field is:
    http://en.wikipedia.org/wiki/Killing_vector_field
     
  14. Apr 8, 2013 #13
    I'm happy with Killing vector fields, but the familiar Killing vector fields of GR generate isometries *of spacetime*.

    However, Smolin says "there are no Killing vector fields or conformal Killing vector fields on this configuration space of general relativity".

    I was thinking maybe when he mentioned the "configuration space of GR", that he was refering to something like Wheeler's superspace. It has a metric (the supermetric), and hence it has the concept of Killing vector fields. But I've never heard a statement like that before in this context. It was supposedly a theorem due to Karel Kuchar.

    However, "configuration space" may have been misleading and he may have just meant something like "cosmological metrics don't admit Killing vectors".
     
  15. Apr 8, 2013 #14

    Chalnoth

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    I think it's a statement that you can always generate a killing vector field locally, or in certain special cases where there is a high degree of symmetry, but you can't apply one to all of space-time (at least not in an expanding universe).
     
  16. Apr 8, 2013 #15
    Here is a link for those interested:
    https://www.amazon.com/Time-Reborn-Crisis-Physics-Universe/dp/0547511728/ref=tmm_hrd_title_0

    It's great to see that they have a Kindle version too:
    https://www.amazon.com/Time-Reborn-Physics-Universe-ebook/dp/B00AEGQPFE/ref=tmm_kin_title_0

    I haven't managed yet to watch the video or read reviews, but for now I'd just like to ask if ideas by Smolin are any near to ideas by Barbour?

    Barbour's book from 2001 titled 'The End Of Time', link:
    https://www.amazon.com/The-End-Time...tmm_hrd_title_0?ie=UTF8&qid=1365453762&sr=1-1
     
    Last edited by a moderator: May 6, 2017
  17. Apr 8, 2013 #16
    I havent had a chance to watch the video yet, but it seems that Smolin is saying the opposite to Barbour who argues time is an illusion. Is that correct?
     
  18. Apr 8, 2013 #17
    This is very interesting to me. Does anyone have a list of physical laws and/or constants that may have, or will change from the BB until now, and into the very distant future?
     
  19. Apr 8, 2013 #18

    marcus

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    That seems correct, though someone who knows Barbour's position on time better than I do should probably answer. For Smolin time is real and fundamental. Not an illusion.

    There is a slight chance that the difference is semantic however. I have to go, back later to address this possibility.
    Back now. I don't really know enough to speculate properly but the way it could turn out to more of a semantic difference is that both are talking about change as being fundamental. That is, no "block universe". So there is no "fourth dimension". In that sense Barbour might say that "time" the fourth dimension does not exist. There is the world, and it changes, and Barbour in a purely classical non-quantum way can show you how, by watching dynamical systems change, you can see time being measured out by change.

    Smolin is certainly more ambitious in that he wants physical law to emerge and quantum probabilities, he wants the whole business to arise from very simple primitives: a set of primitive events that keeps on growing as existing events cause the next generation of events.

    But it seems that for him also there is no block, there is no fourth dimension, there is only a world that keeps changing. So change is the real thing for him (just as I think it may be for Barbour) the difference could be, primarily, that Smolin calls this process of change "time" and Barbour does not call it "time". A basically semantic difference not a deep philosophical opposition, IOW. Just a two cents worth of guess.

    The thing to remember though is that whatever their basic fundamental similarities/differences, Smolin is trying for much much more. He is trying to schematize the whole caboodle, explain why the Laws are these Laws and not some other Laws, and how they came to be, from an extremely simple generic kit of primitives. It is wildly ambitious and so, in that sense, not to be compared with Barbourism.
     
    Last edited: Apr 8, 2013
  20. Apr 8, 2013 #19
    I thought that space and time had no properties and no real existence of their own, unlike sub atomic particles of ponderable matter. All the Physics we have is based ultimately on the way all these particles interact with each other. Their fields and energies and relative locations create the illusion of space and time in our minds like an electron beam creates the illusion of a picture on a CRT.

    A specific Time isn't a location that you can ever travel back to in a time machine, it is an exact position, state and energy of a virtually infinite number of particles thoughout the whole cosmos. Hence reordering this condition is the only way to go back in time, which of course is effectively impossible.
     
  21. Apr 9, 2013 #20
    Actually, I think Smolin was referring to symmetries of superspace (or lack thereof!), since this is what Kuchar was talking about in this abstract

     
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