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31 Dimensionless Constants-Wilczek, Tegmark, Aguirre, Rees

  1. Nov 29, 2005 #1

    marcus

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    31 Dimensionless Constants--Wilczek, Tegmark, Aguirre, Rees

    http://arxiv.org/abs/astro-ph/0511774

    Dimensionless constants, cosmology and other dark matters
    Max Tegmark (MIT), Anthony Aguirre (UCSC), Martin Rees (Cambridge), Frank Wilczek (MIT)
    29 pages, 12 figs
    "We identify 31 dimensionless physical constants required by particle physics and cosmology, and emphasize that both microphysical constraints and selection effects might help elucidate their origin. Axion cosmology provides an instructive example, in which these two kinds of arguments must both be taken into account, and work well together. If a Peccei-Quinn phase transition occurred before or during inflation, then the axion dark matter density will vary from place to place with a probability distribution. By calculating the net dark matter halo formation rate as a function of all four relevant cosmological parameters and assessing other constraints, we find that this probability distribution, computed at stable solar systems, is arguably peaked near the observed dark matter density. If cosmologically relevant WIMP dark matter is discovered, then one naturally expects comparable densities of WIMPs and axions, making it important to follow up with precision measurements to determine whether WIMPs account for all of the dark matter or merely part of it."

    31 fun numbers that determine the universe:smile:

    EDIT BTW the first physics blog to flag this paper was Christine Dantas "Background Independence". She's alert.
    http://christinedantas.blogspot.com/2005/11/salad-of-dimensionless-constants.html
    Looks like she posted at 9AM GMT Wednesday 30 November.
    Cosmic Variance was nowhere in sight, Peter Woit didnt notice
    The new physics blog Aggregate called "Mixed States" posted feed from Christine soon after, maybe a couple of hours.
    http://mixedstates.somethingsimilar.com/
    also this address
    http://somethingsimilar.com/mixedstates/

    I think it is going to be a major paper, not for anything new it says but because of being monumentally thorough in laying out the fundamental constants, with current estimates of their values, and going massively into all the interrelation and derived detail. And for temporarily defining the basic goal of physics and cosmology to explain these 31.

    or, alternatively, if we decide to give up the quest to explain them, then it shows us just what we are giving up on----so at least we have a clear idea of what we are admitting to be imponderable to us

    so this paper can play a kind of landmark or benchmark role
     
    Last edited: Nov 30, 2005
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  3. Nov 30, 2005 #2

    marcus

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    Last edited: Nov 30, 2005
  4. Nov 30, 2005 #3

    marcus

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    Tegmark et al is defective in a sense

    The Tegmark et al "Dimensionless Constants" paper is defective in a sense.

    It leans towards an untestable multiverse picture (involves giving up efforts to explain with a predictive model) and DOES NOT DISCUSS an alternative TESTABLE multiverse conjecture that Smolin has offered.

    the Smolin testable multiverse conjecture says the 31 numbers EVOLVED to their observed values because they promote FECUNDITY---they favor a longlived cosmos with lots of matter that is able to condense and eventually make black holes.

    each stellar-mass black hole sprouts a new tract of spacetime, with its own inflationary (matter-yielding) epoch, and eventually (if the parameters favor condensation) the formation of black holes and further branches of spacetime.

    One could REFUTE the Smolin conjecture if one could show that some of these 31 numbers are not as favorable as they could be to a long-lived universe making lots of black holes----that a minor adjustment of one or more of them would increase black hole fecundity.

    This conjecture (called CNS, cosmic natural selection) at least PREDICTS things that one can test by observation. And AFAIK it has not yet been refuted empirically.

    So by rights Tegmark et al should have described and discussed this CNS conjecture also ALONG WITH the untestable, unpredictive multiverse scenario (eternal multi-bubble inflation) which they focus on.

    Their focusing on multi-bubble inflation----where the 31 numbers in our bubble just happen to be what they are----without discussing a testable alternative is a serious flaw in the Tegmark et al paper.

    That is too bad, I expect better of Frank Wilczek.

    (Tegmark, after reading his Scientific American article on Multiverses, I do not expect high quality thought from----though attractive enough as a popular writer and personality. But Wilczek is someone who has earned solid respect, and not just because of his Nobel prize :smile: )

    Well let us see what venue Lee Smolin chooses to reply, if he does.

    A relevant Smolin paper for Tegmark et al to have cited is

    Scientific Alternatives to the Anthropic Principle
    http://arxiv.org/abs/hep-th/0407213
     
    Last edited: Nov 30, 2005
  5. Dec 1, 2005 #4
    Marcus great paper, I have downloaded it, but I have a backlog of papers so I have not fully read all its contents. The Smolin conjecture (as I see it from your description above?) about Blackhole evolution? ,stellar-mass blackholes, could be a "SECOND-GENERATION" process, and are thus not the same as first-generation "Galactic-Blackholes"? from Tegmark work earlier, I do believe that there is a significant connection with regard to Singularity signature for evolving processes.

    Smolins model takes certain values of BH spacetime's (Galactic-Core's) and resolves a lot of Universal Paramiters, by its association within inflationary models?
     
  6. Dec 1, 2005 #5
    Hi Marcus and Spin Network

    I find this paper quite interesting, and the work that evidently went into the listing of parameters in the opening tables is very useful, I think. Or at least, I find myself wanting to study up on coupling constants, matrix angles, and Higgs coefficients. I am going to google some of the terms and see what I find.

    I am not qualified to comment on the rest of the paper, which has to do with cosmological constraints, as far as I can understand it. But the tables are an excellent summary place to start anew....a kind of landmark, as you said above, Marcus.

    Personally my interest is in the indications for geometry at just below the Fermi scale, and talk of angles and matrices makes me think that looking for geometry in such small spaces may not be entirely lunatic.

    Thanks for posting this here, Marcus, and thanks to the authors.

    Richard
     
  7. Dec 1, 2005 #6

    marcus

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    Hi Richard
    :smile:
    thought you might like this one
    intrinsic proportions in nature
    parameters of reality
    or at least one possible (provisional) version
    notice they use Planck units where necessary---some footnote about that

    glad you had a look

    ==========REPLY BY EDIT================

    Since I still have time to edit i will reply to the next post here.

    Hi selfAdjoint

    ah so!

    What are some of the other pet notions? I am not familiar with Aguirre's and Rees' favorites. I assume Tegmark has the eternal inflation bubble-multiverse bee in his bonnet. But even there I'm not altogether sure.

    so the paper resembles the work of a committee representing different interests!
     
    Last edited: Dec 2, 2005
  8. Dec 2, 2005 #7

    selfAdjoint

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    One of the things that got me was the four big name authors, and when you dig into the paper you find that each of them is pushing a pet idea. For Wiczek fo example, it's axions.
     
  9. Dec 2, 2005 #8
    Lord Rees has a book out called, IIRC, "Just Six Numbers," which presents the idea that small changes in some fundamental constants would cause the universe to be fatally inimical to the evolution of life. Probably the idea goes back before the book was published, but the book was my introduction to that method of analysis.

    I thought it was interesting but not really very carefully considered. It does illustrate the functions of the basic constants in cosmology by showing what would happen if they were slightly different, but it makes no attempt, as I recall, to explain why the constants are what they are.

    The current arguments about anthropery and landscape and design all came after that, at least in my experience, but I wasn't watching very closely back then. Anyway my interest was towards identifying the parameters as we know them and then looking for relationships between them. Still is.

    To that end, I wonder if the list of 31 could be reduced further by showing cases where one parameter is dependent on or related to (covarient with?) another. Anyway that is my current direction of investigation.
     
  10. Dec 2, 2005 #9

    selfAdjoint

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    Richard the paper does discuss a lot of constants that are dependent on the 31. Also we shouldn't take this list of 31 as cast in aere perennis. The authors state this list was arrived at as a simple one and specify the assumptions they made to reach it; others wanting to emphasize other facts might reach a slightly different choice, in which some of the 31 are expressed as dependencies on the new ones.
     
  11. Dec 3, 2005 #10
    Thanks sA.

    http://en.wikipedia.org/wiki/Weinberg_angle

    gives reference to:

    http://www.slac.stanford.edu/exp/e158/

    At SLAC site I read a doctoral thesis,
    A precision measurement of the Weak Mixing Angle in Moller Scattering,
    by Klejda Bega, a member of the group that ran the experiment.

    Notes in quote and paraphrase:

    Weinberg angle theta_w, the weak mixing angle from the Abdus-Salam theory of the electroweak force shows a relationship between W and Z boson masses which varies as a function of momentum transfer Q. Measured in e-e+ collider at 91.2 GeV/c, the mass of the Z. Collision shows parity iolation in e- scattering (Moller).

    In SLAC E-158 an accelerated polarized e- beam hits a liquid hydrogen target, and the parity violating asymmetry occurs in the scattering rate of left versus right polarized e-.

    It seems to me that the very small difference angle between L and R e- might be due to the residual energy in the liquid hydrogen, but I have made no calculations to show the contribution would be to scale. The electrons in the hydrogen are presumably in a low energy state due to the cold, but then shouldn't they have some momentum to contribute to the spin? If most of the e- are in the same quantum state, namely the lowest possible one, then all of their spins would be the same? In a sense they are polarized also, or at least a significant percentage of them could favor one spin state over the other. Then they would add a little energy to the beam electrons with the opposite spin and take a little from the beam electrons with the same spin, causing the asymmetrical angle?

    I don't recall that Dr. Bega said anything about the residual energy in the target spin, but I could have missed it. Or maybe it would be in one of the other thesis that are presented. I suppose I should read them all but it took me all evening to read this one, and I want to get on to the neutrino parameters.

    Corrections? Does anyone know if the target spin is negligible?

    Thanks,

    Richard
     
    Last edited: Dec 3, 2005
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