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Cosmic Natural Selection

  1. Apr 19, 2005 #1

    marcus

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    Cosmological Natural Selection is a testable idea for explaining why the constants in physics and cosmology----the parameters of the standard models used in the two fields----have the numerical values they do.

    I expect it's important enough so that it deserves a more transparent thread heading than "Cns" which is the title of the thread Chronos already started.

    CNS has been proposed as a scientific alternative to "Anthropic" views, according to which the values of the constants do not require a mechanism to explain them because if several of the key numbers were substantially larger or smaller we would not be here to observe it!

    Contrary to "Anthropic" (non?)explanations, the CNS idea offers an evolutionary mechanism by which the constants may have converged on their observed values, in a fashion which has nothing to do with life or consciousness. Nothing to do, that is, except having incidentally provided the conditions needed for life as we know it as kind of side effect, or byproduct.

    And the idea may be wrong, which, curiously enough, is a virtue. CNS seems able to generate predictions ruling out certain observations or experimental outcomes in the future, which, if they WERE seen, would refute CNS. this "falsifiability" is the hallmark of a scientific theory---it is predictive in the sense that there are some outcomes of future experiments which it cannot accomodate. If a theory is mushy enough to accomodate any conceivable outcome of future experiments intended to test it, then it has no predictive value. (Try to imagine performing an experiment and obtaining a result that is incompatible with the existence of conscious life! :smile:) By contrast, CNS seems to to be predictive, hence part of empirical science instead of, say, philosophy or religion.

    I'm intending this to be an informational thread about CNS, so for starters here is a short reading list borrowed from the LQG link-basket
    https://www.physicsforums.com/showthread.php?p=527991#post527991

    1.these two papers, and the references therein, discuss the removal of the classical BB ex-singularity in a range of cases that has gradually extended the generality of Bojowald's initial 2001 result.

    http://arxiv.org/abs/gr-qc/0402053
    Loop Quantum Cosmology: Recent Progress
    Martin Bojowald
    17 pages, 2 figures, Plenary talk at ICGC 2004

    "Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from general relativity: The quantum theory is free of singularities, and there are new phenomenological scenarios for the evolution of the very early universe including inflation. We give an overview of the main effects, focussing on recent results obtained by several different groups."

    http://arxiv.org/abs/gr-qc/0503020
    The Early Universe in Loop Quantum Cosmology
    Martin Bojowald
    10 pages, 3 figures, plenary talk at VI Mexican School on Gravitation and Mathematical Physics, Nov 21-27, 2004

    "Loop quantum cosmology applies techniques derived for a background independent quantization of general relativity to cosmological situations and draws conclusions for the very early universe. Direct implications for the singularity problem as well as phenomenology in the context of inflation or bouncing universes result, which will be reviewed here. The discussion focuses on recent new results for structure formation and generalizations of the methods."

    2. these papers, and references therein, go towards understanding the BH ex-singularity and showing that it evolves into the BB ex-singularity:

    http://arxiv.org/abs/gr-qc/0503041
    A black hole mass threshold from non-singular quantum gravitational collapse
    Martin Bojowald, Rituparno Goswami, Roy Maartens, Parampreet Singh
    4 pages, 3 figures

    "Quantum gravity is expected to remove the classical singularity that arises as the end-state of gravitational collapse. To investigate this, we work with a simple toy model of a collapsing homogeneous scalar field. We show that non-perturbative semi-classical effects of Loop Quantum Gravity cause a bounce and remove the classical black hole singularity. Furthermore, we find a critical threshold scale, below which no horizon forms -- quantum gravity may exclude very small astrophysical black holes."

    http://arxiv.org/abs/gr-qc/0504043
    Quantum Gravitational Collapse
    Leonardo Modesto
    13 pages

    "We apply the recent results in Loop Quantum Cosmology and in the resolution of Black Hole singularity to the gravitational collapse of a star. We study the dynamic of the space time in the interior of the Schwarzschild radius. In particular in our simple model we obtain the evolution of the matter inside the star and of the gravity outside the region where the matter is present. The boundary condition identify an unique time inside and outside the region where the matter is present. We consider a star during the collapse in the particular case in which inside the collapsing star we take null pressure, homogeneity and isotropy. The space-time outside the matter is homogeneous and anisotropic. We show that the space time is singularity free and that we can extend dynamically the space-time beyond the classical singularity."

    3. if the models of BH collapse and BB expansion can be joined in theory then one can take seriously the CNS (cosm. nat. selection) hypothesis as a way of understanding why the basic constants in the Standard Models are what they are. The CNS theory can be tested empirically by observation and experiment. This paper discusses CNS:

    http://arxiv.org/abs/hep-th/0407213
    Scientific alternatives to the anthropic principle
    Lee Smolin
    for "Universe or Multiverse", ed. by Bernard Carr et. al., to be published by Cambridge University Press.

    "It is explained in detail why the Anthropic Principle (AP) cannot yield any falsifiable predictions, and therefore cannot be a part of science. Cases which have been claimed as successful predictions from the AP are shown to be not that. Either they are uncontroversial applications of selection principles in one universe (as in Dicke's argument), or the predictions made do not actually logically depend on any assumption about life or intelligence, but instead depend only on arguments from observed facts (as in the case of arguments by Hoyle and Weinberg). The Principle of Mediocrity is also examined and shown to be unreliable, as arguments for factually true conclusions can easily be modified to lead to false conclusions by reasonable changes in the specification of the ensemble in which we are assumed to be typical.
    We show however that it is still possible to make falsifiable predictions from theories of multiverses, if the ensemble predicted has certain properties specified here. An example of such a falsifiable multiverse theory is cosmological natural selection. It is reviewed here and it is argued that the theory remains unfalsified. But it is very vulnerable to falsification by current observations, which shows that it is a scientific theory.
    The consequences for recent discussions of the AP in the context of string theory are discussed."
     
    Last edited: Apr 19, 2005
  2. jcsd
  3. Apr 21, 2005 #2

    ohwilleke

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    A few points.

    1. Publishing an article in an Intelligent Design showpiece book, even if it says that CNS is better than AP, is a pretty counterproductive activity.

    2. Smolin's article claims to be based on a conjecture by J.A. Wheeler that all the fundamental constants change when black holes happen. Where does that come from and what does he have to back it up?

    3. Falsifiabilty does not a scientific theory make. A valid scientific theory needs to be an empirically motivated explanation for observed phenomena which explains the data without unnecessary elaboration or extrapolation from known facts.

    I can hypothesize that fairies create stars in nebula by following a formula combining various proportions of atomic gases, that the fairies are not themselves luminous and contribute immaterially to the total mass of the nebula making them hard to detect by gravity, that they are corporal and as easy to observe as a ferret, and that they move a speeds less than 1% of the speed of light in a vaccum. I can further hypothesize that fairies particularly like galactic clusters and that their presence accounts for the exceptionally high dark matter content of such structures. I can further show, that the fairie theory makes cosmological inflation unnecessary because eternally existent fairies could have through intentional action achieved events that blind graviational forces would not. I could then recast all of stellar evolution as a theory of fairie behavior.

    We haven't gotten close enough to any nebula to falisfy that theory. But, certainly it could be falisfied, in principle anyway, by going to a nebula and looking for them where they are ubiquitous. But, I think you'd agree that this is still not a scientific theory.

    Scientists have never observed fairies, no experiement has ever predicted the existence of a fairie. Likewise, science has never observed a change in a physical constant and no experiment has ever indicated a change in a physical constant. Maybe a few French scientists who've had too much abisinthe have thought about the fairie idea (this is called Green Fairie Theory) and even played it out for a while without finding any obvious objections, but certainly no one is rushing to show how fairie theory is falisfiable, while AP is not, in an Intelligent Design anthology.

    4. Arguing from the credibility of the author doesn't count for much either.

    Newton is one of the most renounced scientists for hundreds of years either side of his birthdate. His theories are still taught in college physics and the foundations of his ideas are still visible even in modern physics elaborations of those ideas. But, he also spent huge amounts of time working on heretical theology and alchemy. Even the best scientists get bad ideas from time to time.
     
    Last edited: Apr 21, 2005
  4. Apr 21, 2005 #3

    Garth

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    Another point.
    CNS is not contrary to anthropic explanations, it is a possible anthropic explanation! If we ask the question: "Why have physical constants the values they have?" CNS suggests the answer: "Because those constants maximise the production of black holes in any given universe after a sufficient number of 'cosmic' iterations. "

    The AP evokes a set of possible and alternative explanations:
    1. It is a brute fact, a 'fluke'.
    2. It is a selection effect. There is a multiverse and we are in this universe because we can be in no other.
    3.There is an unspecified mechanism that determines the constants to be so.
    4. Observers today collapse the wave function of the entire universe so that it allows the existence of observers today; this may be one possible mechanism required by 3.
    5. It is the product of design.

    CNS is also one of the possible mechanisms required by response 3.

    Finally, is not the fact that this set of values "incidentally provided the conditions needed for life" rather a coincidence, indeed an anthropic coincidence?

    Garth
     
    Last edited: Apr 21, 2005
  5. Apr 21, 2005 #4

    ohwilleke

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    I agree with Garth. CNS is a subtle version of an AP argument.
     
  6. Apr 21, 2005 #5

    marcus

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    I dont agree, Ohwilleke, and do not see CNS as a version of AP. However since Garth says CNS belongs to his AP version #3, let us look at it.
     
  7. Apr 21, 2005 #6

    marcus

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    Garth alternative #3 is not the AP as commonly understood.

    for centuries the goal of physics theory has been to find mechanisms determining the features of the world (the distances and periods of planets, the wavelengths of the hydrogen spectrum) and to reduce the number of constants

    a longstanding goal of string theory was to reduce the parameters down to one, to derive the other constants from the string constant.

    theorists have traditionally asked "why have the constant proportions of nature the values they do?" and have traditionally searched for
    "unspecified mechanisms that determine" the proportions of nature to be as they are.

    this goes back a long time and has nothing to do with the "anthropic" (lack of) principles, which distract people from seeking mechanisms determining the constants by offering a phony explanation (that the constants have to be what they are because of something to do with conscious life)

    so Garth #3 doesnt cut the mustard and I remain skeptical of his effort to include
    CNS under the AP tent.
     
  8. Apr 21, 2005 #7

    marcus

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    Dear Garth, if you want to take it as a proof that God loves us because the constants of nature, as optimized for black hole production, accidentally allow carbon-chemistry and life, that is FINE and I will applaud you as a man of reverence and devout spirituality.

    what I care about is that people should seek mechanistic explanations for why the laws of nature and the proportions built into them (the dimensionless parameters) are as they are

    I shall hope that people will always be dissatisfied with the phony explanation that the values of the constants somehow reflect our existence

    and I will be happy with whatever theological spin anyone wants to put on the models being tested.
     
  9. Apr 21, 2005 #8

    Chronos

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    I think selection effects is a very powerful argument. All that really says is, at some level, there is a deeper reason why things [like fundamental concepts] are what they are. To claim otherwise is to say 'chit happens'. And that's not very satisfying, much less scientific. The more important question [to a scientist] becomes what is the deeper reason? The anthropic principle is a pretty weak candidate compared to CNS. The universe was around long before us, or any other probable spectators. It reminds me of the coach joke

    Reporter: "Folks, I'm here with coach [insert favorite] on tonite's show. Coach, what would you say is the most amazing thing you've seen in your illustrious career?"

    Coach: "the thermos bottle"

    Reporter: "What do you mean?"

    Coach: "Put something hot in it, it stays hot. Put something cold in it, it stays cold."

    Reporter: "What is so amazing about that?"

    Coach: "How do it know?"
     
  10. Apr 21, 2005 #9

    turbo

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    Marcus, I have told you about my ferrethropic model and my extreme adversion to the logical extension to the earmitethropic model. I did this in jest, but I am very serious. The idea that anyone can point to the existence of ANY object or ANY lifeform and say "the existence of X is proof that all the cosmological parameters must be as they are" is pretty silly. Actually it's worse than silly, but I'm trying to be nice.

    Let's get pretty basic. If the existence of X and Y arises out of conditions of the Universe A, we might posit that the conditions of Universe A are necessary for the existence of X and Y. If someone tries to claim that the observation of the present-day existence of X and Y places prior constraints on the conditions of Universe A, I've got to ask "what are you thinking?" Humans have existed in this universe for less than an eyeblink in time, and for someone to postulate that the Universe is fine-tuned to produce us is the height of stupidity. If you look at Lee's paper, I think he's got an admirable tongue-in-cheek attitude that challenges Lenny to come up with a viable explanation for the anthropic principle that shows how the Universe must be fine-tuned to produce weak short-lived bags of mobile protein instead of black holes.

    I think Lee is spending just a bit of his scientific "capital" to set the field for the much more important discussion regarding the logical (or not!) extensions that the AP people are making regarding the relationships between basic constants and the "coincidence" that we are here.

    This speaks to a really basic problem of the AP and of intelligent design: "We are here and we see our universe. We think that X, Y, and Z are true, based on what we see. If X, Y, and Z were not true, the universe would be different, and therefore we would not exist. Therefore, we exist because some underlying design made sure that X, Y, and Z were in place, which allows us to exist here and now." I just love it when the entire cosmos conspires to make me exist! It smells like victory! :yuck:
     
    Last edited: Apr 21, 2005
  11. Apr 21, 2005 #10
    Maybe it clarifies things to think in terms of entropy. Obviously, people represent a highly improbable construction since it is more likely that things dissipate. Perhaps the universe that must be chosen from the landscape is the one that allows for such complexities to arise. It may not be human, per se, that are required but constructions that represent a reduction in entropy to balance otherwise too much dissipation. If the physical constants were changed slightly, could complex structure even arise in such a universe? Perhaps the constants are chosen to at least allow for maximum decreases in entropy if the need should arise?
     
  12. Apr 21, 2005 #11

    marcus

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    you have put your finger on a significant issue for the CNS picture of how the universe evolves

    right after the big bang (to the extent that one can see a thermodynamic state where entropy is defineable and makes sense) the entropy would seem to be very low

    at least from our point of view looking back at it in our past

    but prior the big bang, if there was a black hole collapse (as per CNS picture) then it would seem to have very high entropy, at least from the perspective of people outside the hole looking at the event horizon. We normally think of black holes in our universe as having very high entropy.


    if you can picture a timeline or worldline running from those observers (one of them jumps in) down thru the hole and the big bang and thence to us (which I cant. I dont think that is a valid timeline) but if you can picture keeping track of the entropy along that line (which I see problems with) then you find yourself going from seeing a high entropy state (looking at the BH) to a very low entropy state (looking at the fresh universe right after BB). that is supposed not to happen, entropy is only supposed to increase.

    I think the best way to handle this is to clarify in each case who the observer is. Like Crosson indicated, entropy is defined relative to an observer (the log of the number of different states that look the same TO THAT OBSERVER according to what variables that observer can measure, be it pressure volume temperature or whatever.

    the Crosson post I mean is this one:
    https://www.physicsforums.com/showthread.php?p=540380#post540380
    it was in response to a question you raised about entropy in a thread you started, Mike
     
    Last edited: Apr 22, 2005
  13. Apr 22, 2005 #12

    Chronos

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    Good point, marcus. Could the bounce in a gravitational collapse result in a frame dependent measure of entropy? An observer outside the event horizon would measure a huge amount of entropy, while an observer inside the event horizon would measure almost zero entropy. It would make sense as an extension of the equivalency principle.
     
  14. Apr 22, 2005 #13

    marcus

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    I am not quite clear on relating entropy and general relativity (maybe that is an understatement, maybe i am grossly unclear about it:smile:) but I does seem interesting.

    oh yes, the OBSERVER. entropy seems to be rather much in the eyes of the beholder doesnt it?---what level of detail he sees, what he coarse-grains or doesnt.
     
    Last edited: Apr 22, 2005
  15. Apr 22, 2005 #14

    Garth

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    I'm sorry I disagree. My option 3."There is an unspecified mechanism that determines the constants to be so." is the Strong Anthropic Principle. "The Universe must have those properties that allow life to develop within it at some stage of its history." (Barrow & Tipler - The Anthropic Cosmological Principle)

    Another way of seeing this is to say that if there were a multiverse then every universe would be propitious for life, at some stage, out of logical necessity.

    The task would be then to discover what that logical necessity is, i.e. what is the mechanism, in the venerable tradition: "for centuries the goal of physics theory has been to find mechanisms determining the features of the world".

    Such a search and discovery would have no bearing on the question of belief in a 'Creator' or 'Design', which would be an interpretation on the facts, just as is non-belief in the same.
    "I want to know how God created this world. I am not interested in this or that phenomenon, in the spectrum of this or that element. I want to know His thoughts; the rest are details." (A.E.)

    A theist belief would simply be saying that mechanism is "God's way of doing it."

    Garth
     
    Last edited: Apr 22, 2005
  16. Apr 22, 2005 #15

    marcus

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    You seem to me to have made a logical error, Garth. Your post which I quoted was:

    Since you said CNS comes under heading 3, I extracted out

    So far the argumentation does not involve life. CNS is a possible mechanism that determines the values of the constants---OK, so far you havent dragged life in, CNS is determining some numerical values.

    Now you surprise us all and pretend that your alternative 3. (which you stated without reference to life) was meant to be the Anthropic Principle all along.

    ---quote---
    My option 3."There is an unspecified mechanism that determines the constants to be so." is the Strong Anthropic Principle.
    ---end quote---

    Well it simply is not. "To be so" in your earlier post is a shorthand for "to have the values they have".

    So it seems to me you are weaseling, or "zig-zagging". You say something, and then you pretend (or mistakenly act as if) you said something different.
    Zig-zagging can make for a tedious conversation.

    Also I am not sure what you mean by "unspecified", if you want CNS to be included. Granted that the details of the hypothesized connection between BH and BB remain to be worked out (and may indeed fail to work and be rejected!) is a specific mechanism that works in a specified way to determine some numbers. Since it is neither fully specified nor fully unspecified, I suggest that it may be tendentious to include the word "unspecified". So I would put your #3 this way:

    "There is a mechanism that determines the constants to have the values they have."

    This is NOT the Strong Anthropic Principle. CNS treats life as an epiphenomenon (essentially irrelevant side effect, byproduct) and offers to explain the values of the constants by some mechanism without reference to life. Only by zig-zagging can one blur the distinction between CNS and SAP.

    I think I will see how it looks to spell "zig-zag" with a smilie :

    :zzz:ig- :zzz:ag

    hey cool :cool: :tongue2: it works, not a bad way to spell it!
     
    Last edited: Apr 22, 2005
  17. Apr 22, 2005 #16

    ohwilleke

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    Just to be clear, CNS, of course, doesn't flow from the existence of life. But, I think it is fair to call it an AP like theory, because the type of reasoning is similar. Instead of arguing that the universe has the constants it does because conditions life exist, it argues that the universe has the constants it does because things like the frequently distribution of things like black holes are they way that they are.

    Both approaches reverse the plausible order of cause and effect without a very strong motivation for doing so. Both engage in a poorly motivated attempt to create a distribution of possible universes and explain why we are in a particular place in that distribution.

    String theory is doing something far more plausible. It is looking at 26 constants and guessing that there are really hidden relationships among them that allow you to derive most of them from a far smaller number of constants, if you just find the right unifying theory that explains hidden structure beneath the particles and forces which we observe.

    Of course, string theory still leaves you with a handful of constants, but, to the extent that say 23 out of 26 constants are derived from the other three, the room to "fine tune" the universe through "cosmic natural selection" to look like what we see now, is greatly diminished.
     
    Last edited: Apr 22, 2005
  18. Apr 22, 2005 #17

    marcus

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    that is a worthy goal, but as far as I know string fails. there is no accepted value of the string constant, there is no derivation of the constants of the standard model. there are no predictions concerning the results of future experiments.

    indeed the tendency (since the KKLT paper of 2003) of string theorists to give up and appeal to the Anthropic Principle is a sign of desparation, dimming hopes of ever achieving that goal, worthy as it is.

    I hope some completely new approaches are tried and some are more successful! It would be great to reduce the number of constants down to a handful from which all the rest could be calculated!

    that would be great from a CNS viewpoint, one would have fewer undetermined parameters that one has to explain by an evolutionary mechanism :smile:

    I agree, CNS and AP are different. It is also fair to point out the similarities, IF one is also clear about the differences!

    IT IS POSSIBLE TO SHOOT DOWN THE PROPOSITION THAT THE UNIVERSE IS ADAPTED TO BLACK HOLE PRODUCTION. Indeed I would be delighted to hear that some highly reliable observation had ruled out CNS or made it highly unlikely. It is not something that one believes in, it is something that (I hope) will be tested. If it is ruled out (which would be progress according to conventional ideas of science where one proceeds by ruling out successive theories) then other mechanisms for determining the parameters of the prevailing models will, I hope, be proposed and tested in their turn.

    By contrast, it is not possible to shoot down the proposition that the universe is suitable for life, or if you think it is, how do you want to go about it?
     
    Last edited: Apr 22, 2005
  19. Apr 22, 2005 #18

    marcus

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    Ohwilleke it seems to me that CNS makes a strong assertion that the universe is optimized for black hole production. If that were shown not to be the case, i would be inclined to discard it. It would not hold much interest for me, although one could always add some assumptions to "patch up" and salvage the concept.

    SAP, as i take it, only says that the universe permits life, it does not even say it is optimized for life. The existence of life is very difficult to count (except here on earth). The whole thing is a can of worms.

    CNS is dealing with something we can observe all over the place, and count, and where we can hope to calculate how changing a parameter would affect BH abundance.

    We can see lots of black holes. We can judge whether the parameters are optimal to make them abundant. If not, chuck the idea out. If they are optimal, then go figure (make up some explanation, the least bizarre that you can).

    You seem to think that I am "reversing the normal order of cause and effect", or that somehow CNS does this. I am not and it is not. Nor am I trying to persuade you of anything implausible. I dont care whether or not you believe that BH can connect to BB. what I care about is knowing if the Standard Model parameters are optimized for BH production.

    If they are then I would consider that a very remarkable fact requiring explanation.

    I can't imagine you would not agree with the reasonableness of this.

    Just find me one parameter which is not optimized for BH production. In principle it should not be all that hard.
     
  20. Apr 22, 2005 #19

    ohwilleke

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    Before one goes about ruling out theories, one has to make a strong enough case that it should even be considered in the first place. [Time warp here. Your post above wasn't there when I posted this one and I will respond to your post above].
     
  21. Apr 22, 2005 #20

    wolram

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    Do you need a theory that predicts BH production? is not true that any
    dynamic system must have a beginning and an end, cosmology is the only
    science that seems to allow the possibility for perpetual motion, i hope
    this is true in one shape or form.
    But given an attractive force and a limited density area, i guess BHs are
    inevitable.
     
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