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The birth of spacetime atoms as the passage of time

  1. Oct 15, 2014 #1
    http://arxiv.org/pdf/1405.3492v1.pdf

    The birth of spacetime atoms as the passage of time

    The view that the passage of time is physical finds expression in the classical sequential growth models of Rideout and Sorkin in which a discrete spacetime grows by the partially ordered accretion of new
    spacetime atoms.

    "Sorkin’s suggestion that the birth of spacetime atoms correlates with our conscious perception challenges the view that quantum gravity effects can only show themselves as phenomena in regimes far beyond our immediate reach. The idea is that we may have access, through our intimate experience, to a physical phenomenon that is not present in General Relativity but is part of a more complete theory of spacetime. Lest this seem far-fetched, let me introduce an example from history where an everyday human experience was pointing the way to a new understanding of the physical world, but the lack of a theoretical framework in which to situate and understand this experience meant that it remained (as far as I know) un-articulated until the beginning of the twentieth century".

    I don't know the implication but would it possible that time is separated from space? There is an ongoing Double ElectroStatic Ion-Ring ExpEriment, DESIREE-- "ions down to their ground state these ions move around rapidly in random directions, but when we cool them, they form this ring and they slow down, and you would expect that at some point, this ring stops moving".

    I got little information finding related articles. What is the status of the experiment?
     
  2. jcsd
  3. Oct 15, 2014 #2
    Report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. they have produced beams of atomic carbon anions and small carbon anion molecules ( C−n , n = 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 KeV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 KeV C−2 molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s ± 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10−14 mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.
    i got just this much information from web........!
     
  4. Oct 15, 2014 #3

    Doug Huffman

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    You might look to Lee Smolin's Leibnitzian relational space, with a particle's relations with other particles generating the fields to make the relational connections.
     
  5. Oct 15, 2014 #4
    This article contains 0 (zero) formulas :)
    Is it physics or poetry?
     
  6. Oct 15, 2014 #5
    no its not poetry its the information
     
  7. Oct 15, 2014 #6

    marcus

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    I'm missing something. How do you get from Dowker's talk to DESIREE? My hunch is the connection must be very interesting.
    I was delighted with Dowker's talk, her presentation of the Causal Sets understanding of the passage of time is exceptionally fine.
    When you say "finding related articles" the implication is you mean articles related to the ion ring experiment. Are you also looking for articles on Causets? My guess is that you are not---the literature is extensive and in any case Dowker's article reviews the work on this and gives plenty of references.

    In case anyone is new to Causal Sets and wants an introduction there are some video talks on PIRSA by both Dowker and Sorkin. You just have to google "pirsa dowker".
     
  8. Oct 15, 2014 #7

    marcus

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    Galileo sometimes wrote physics in the form of dialogs (imagined conversations between different characters representing different points of view).

    Galileo changed the FRAMEWORK in which motion is understood, I think.

    You cannot write formulas until you have a framework. They won't mean anything to people. What framework do you know for understanding the passage of time that we experience, and the "now" that we experience? For that one needs a new conceptualization that goes beyond the time-honored Block Universe. One needs to describe the geometry of the universe as a PROCESS in which there is a clear place for the present moment.

    In fact Sorkin, Dowker and others do have formulas! See some of the references in her introductory talk. Or see the Perimeter Institute talks on Causal Sets (google "pirsa dowker"). They prove stuff mathematically. But their equations would not make sense to an audience encountering Causets for the first time. So I think she was right to leave equations out of her introductory talk. It was given at the 2012 Capetown conference mentioned in the abstract here:

    http://arxiv.org/abs/1405.3492
    The birth of spacetime atoms as the passage of time
    Fay Dowker
    (Submitted on 14 May 2014)
    The view that the passage of time is physical finds expression in the classical sequential growth models of Rideout and Sorkin in which a discrete spacetime grows by the partially ordered accretion of new spacetime atoms.
    15 pages, 1 figure. Article based on an invited talk at the conference "Do we need a physics of passage?" Cape Town, South Africa, 10-14 Dec 2012. Submitted for publication in Annals of the New York Academy of Sciences (2014)
     
    Last edited: Oct 15, 2014
  9. Oct 15, 2014 #8

    Hi Marcus,

    Intriguing actually. I was watching an episode of through the wormhole(...I know! But heck, I did it anyways). It was after Rovelli's part that they feature about Fey's version. She's suggesting a very odd way of treating spacetime and it is not hard to imagine. We are used to the standard picture of time/space that is inextricably joined--frozen block of space time landscape. She is proposing that our universe is like a growing pile made of quantum grains of space and time. At fundamental, tiny scales, it's grainy and particulate. At large scales, it appears smooth and continuous. Thats her idea of a granular model of spacetime--spacetime atoms(ignore the atom part lol). Weird part is she is treating spacetime as fundamentally atomic that is forever growing (Kinda cool imagining in my head) and she called those connected sequences of events-- Casual set. The birth of this atom(present) is the passage of time and they pile up--(past experience) like an endless rain of events. Surprisingly enough, there is an experiment to test whether ions show sign of time jitters using calcium ions cooled down to their ground state and hopefully find effects of space seperated from time or whether spacetime can indeed generate itself in quantum dips. Well, i have also similar formulation but instead of jitters of spacetime atoms. I consider the jitter as visual mirages caused by dilation. Well. Enough about me since it is not allowed.
     
    Last edited: Oct 15, 2014
  10. Oct 15, 2014 #9
    Yes, understood.
    However, the only falsifiable prediction of this theory is... the "feeling" of passage of time. Seriously, I can accept that (in fact I think consciousness plays some role in physics - at least in the unfair sampling of reality), but I am afraid that change of paradigm would be too radical for the modern science.

    There is a second problem nobody had mentioned. "to grow" means "to change size in time". However, spacetime itself can't grow because there is no time until it had grown. Unless you somehow use a *second* time (in the same manner as another *time* is used in the explanations of the transactional interpretation ("and *then* wave comes back to the source backward in time))

    Finally, what's about the spacetime atoms after "NOW" passes? Are the langolieres responsible for the destruction of spacetime atoms? :)
     
  11. Oct 15, 2014 #10
    I can follow some of the equation(general). The diagram is also easy to follow for laymen---Lorentz invariant integrated in Minkowski space as points. The only problem is what it really meant is kinda murky lol..

    http://loops05.aei.mpg.de/index_files/PDF_Files/dowker.pdf
     
  12. Oct 15, 2014 #11

    marcus

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    Hi Tz, I think part of the difficulty may be verbal---Julcab used the image of a growing pile of grains of space-time--- and you say "grow" means to change size IN time.

    Dowker repeatedly stresses the insistence that there be no global universal time. But this process of adding grains to the pile (which does not happen IN time) is itself a kind of pro to-time, or pre-time. It is a process from which the local experience of time passage can arise.

    BTW did you look at her paper and in particular did you examine Figure 1? A Causal Set is a causality STRUCTURE which can be diagrammed as a tree graph showing which events (grains) are causally related to which others. Dowker says that the analog of GENERAL COVARIANCE in the Causet picture is the condition that it does not matter in which order the tree diagram is built up. And that is what Figure 1 illustrates. The order of growth, indicated by the numbers, does not matter. The two trees are the same.

    This is analogous to the GR thing where two metrics are equivalent, and represent the same geometry, if one is merely a coordinate transformation of the other---socalled "diffeomorphism invariance" or "general covariance".

    Here's something interesting: there's a theorem that a GR continuous 4D geometry, a metric, is 9/10 causality structure (the light cone information, what is in the past light cone of what) and 1/10 volume information. At each point the metric has 10 degrees of freedom, it is a 4x4 matrix with some symmetry so that there are only 10 independent variables. The theorem says that specifying the lightcones determines 9 of the 10 and local volume information determines the rest. For specifics you should look at the references which Dowker gives for this. IIRC one of the people involved in proving the theorem was Sorkin. It kind of a famous theorem--I've never gone through the proof.
     
  13. Oct 15, 2014 #12

    marcus

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    In this connection I should mention one of the papers on the 3rd quarter MIP poll:
    https://www.physicsforums.com/threa...4-mip-most-important-qg-paper-part-ii.773590/
    (because of format limitations I had to divide the list into two segments, this paper was on Part II of the poll)

    http://arxiv.org/abs/1407.0032
    Spin foam models as energetic causal sets
    Marina Cortês, Lee Smolin
    (Submitted on 30 Jun 2014 (v1), last revised 28 Jul 2014 (this version, v2))
    Energetic causal sets are causal sets endowed by a flow of energy-momentum between causally related events. These incorporate a novel mechanism for the emergence of space-time from causal relations. Here we construct a spin foam model which is also an energetic causal set model. This model is closely related to the model introduced in parallel by Wolfgang Wieland in arXiv:1407.0025, and this construction makes use of results used there. What makes a spin foam model also an energetic causal set is Wieland's identification of new momenta, conserved at events (or four-simplices), whose norms are not mass, but the volume of tetrahedra. This realizes the torsion constraints, which are missing in previous spin foam models, and are needed to relate the connection dynamics to those of the metric, as in general relativity. This identification makes it possible to apply the new mechanism for the emergence of space-time to a spin foam model.

    16 pages, 4 figures.

    What I want to say is that we know a space-time geometry is a causal structure which we can imagine as a kind of graph illustrating a partial ordering among events or grains PLUS volume information. Now Cortês and Smolin have imagined the volume information flowing through that graph as a kind of geometric energy or momentum. So they have a model of geometry as "energetic causal set".

    And it turns out that something analogous was worked out by Wolfgang Wieland in the LQG context: a kind of spin foam model with a new conception of geometric momentum flowing through it. So Cortês and Smolin are pointing out the similarity.

    1. it seems like either or both of these models should be close to recovering GR in the continuum limit, or anyway in some appropriate limit, because they have both the causality and the volume information which constitute continuum geometry.

    2. it seems that at least the causal set picture, and perhaps also the similar spinfoam one as well, have a natural way to represent NOW and the passage of time.

    Because as Dowker's paper explained the causal set is constantly adding more grains. In that picture the PAST is a crystallized BLOCK but the future is not part of the picture, there is only the (presumably roughly 3D) surface of the block past where new grains are constantly being added.
    this constant addition is what gives the local experience of passage of time.

    However the order in which grains are added is, as Dowker's paper states, pure gauge---physically meaningless. See her Figure 1. This is the analog in Causet of the General Covariance of GR an it is apparently an important principle, possibly nontrivial or hard to assimilate at first. If it were not she probably wouldn't have devoted that figure to it.
     
  14. Oct 16, 2014 #13
    I understand that it does not matter in which order the tree diagram is built up., but it just means that a set is weakly ordered. Weakly ordered sets are perfectly consistent with Block time. So if causet *always* exists (*always* in a timeless, mathematical sense) then we have a block time, and there is no explanation of the "feeling of passage of time".

    If these structures "crystallize", then you do need a second proto-time, or pre-time, how you call it.

    Also note that when you say that "2 diagrams are equivalent", you are talking about the *complete* diagrams, not partial diagrams, where "crystallization" had stopped at some state - because partial diagrams can be not equivalent (they can miss different subbranches). So, you can say that the diagrams are equivalent only from a position of block time, viewing them as mathematical object.
     
    Last edited: Oct 16, 2014
  15. Oct 24, 2014 #14

    marcus

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    "..it just means that a set is weakly ordered."​

    the tree diagrams in Dowker's paper do not represent weakly ordered sets. Look up w.o. sets on Wikipedia, they are totally ordered except for ties.
    The causal sets we are talking about are partially ordered sets (look up on Wikipedia) a mathematically different concept.
    I don't think you can say that p.o. sets are "perfectly consistent with Block time".
    One of the main points about the causal set approach is that it is not equivalent to the block universe picture. There is no foliation into physically meaningful 3D slices.

    "If these structures "crystallize", then you do need a second proto-time, or pre-time, how you call it."​

    No. Don't think of the assembly of a causet as physical. It is just an abstract series of steps, which can be done in many different orders. Not necessary that it could be made to correspond to physical time. "crystallize" is metaphorical not meant to suggest a physical process happening in time.
    If it makes you think of a physical process then don't use the word.

    "Also note that when you say that "2 diagrams are equivalent", you are talking about the *complete* diagrams, not partial diagrams, where "crystallization" had stopped at some state - because partial diagrams can be not equivalent (they can miss different subbranches). So, you can say that the diagrams are equivalent only from a position of block time, viewing them as mathematical object."​

    The 2 diagrams are the same if they are the same as partially ordered sets. There is no "position of block time" because posets are not blocks.
    Look at Dowker's figure of the two trees. The NUMBERING is not part of the poset. The two trees are the same, just differently numbered.
    That is her point. Two posets, identically the same as posets, can be assembled conceptually by the mathematician in different sequence of moves and so would have different numbering. But different numbering is physically meaningless (as she says, "pure gauge")
     
    Last edited: Oct 24, 2014
  16. Oct 24, 2014 #15

    marcus

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    Dowker's May 2014 essay is potentially very useful, I think. I'll give the link to it again and a couple of quotes.
    http://arxiv.org/pdf/1405.3492v1.pdf
    The birth of spacetime atoms as the passage of time
    Fay Dowker

     
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