Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Threesphere world could have come from hole ( best-fit radius 130 billion LY)

  1. Jan 26, 2007 #1

    marcus

    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    Threesphere world could have come from hole ("best-fit" radius 130 billion LY)

    Ned Wright just posted this paper where he says the best-fit Omega is 1.011.

    It is still consistent to imagine that space is flat infinite with Omega exactly 1, but that is not what fits the data best. In other words, if you like thinking of space as infinite and Euclidy that is fine and no reason you should re-arrange your mind.

    But Wright took all the available---WMAP, supernovae, gammarayburst, galaxy-counts etc.----and came up with a best-fit that makes space a BUMPY THREESPHERE WITH RADIUS (of curvature) 130 BILLION LIGHTYEAR.

    If you take that seriously then the world could have sprouted from the bottom of a black hole. :smile: So it may be time to get used to the idea.

    http://arxiv.org/abs/astro-ph/0701584
    Constraints on Dark Energy from Supernovae, Gamma Ray Bursts, Acoustic Oscillations, Nucleosynthesis and Large Scale Structure and the Hubble constant
    Edward L. Wright (UCLA)
    16 pages Latex with 8 Postscript figure files

    "The luminosity distance vs. redshift law is now measured using supernovae and gamma ray bursts, and the angular size distance is measured at the surface of last scattering by the CMB and at z = 0.35 by baryon acoustic oscillations. In this paper this data is fit to models for the equation of state with w = -1, w = const, and w(z) = w_0+w_a(1-a). The last model is poorly constrained by the distance data, leading to unphysical solutions where the dark energy dominates at early times unless the large scale structure and acoustic scale constraints are modified to allow for early time dark energy effects. A flat LambdaCDM model is consistent with all the data."
     
    Last edited: Jan 26, 2007
  2. jcsd
  3. Jan 26, 2007 #2

    mathman

    User Avatar
    Science Advisor
    Gold Member

    What is the error estimate for 1.011? If exactly 1 is within range, then some of this speculation is premature.
     
  4. Jan 26, 2007 #3

    marcus

    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    I've seen an errorbar of [1.008, 1.037] in another paper related to this one.
    That was a 68 percent confidence interval in the official presentation of the Third Year WMAP data March 2006 by Spergel et al. (see page 54 figure 17)
    However according to me that doesnt prove anything. Omega could still be exactly one or even less than one.

    So indeed, if you care about that, one can find error-bars in which exactly 1 is NOT in the range, because the error bar is all on the positive side of one. But I would say that not only "some of this speculation" but ALL this speculation is premature! That is what speculation is for! :smile: It is SUPPOSED to be premature and it plays a necessary role in people's thinking.

    Clearly if you like to think of the universe as infinite you should continue thinking of it that way. Only just for a second perhaps you should entertain the possibility that it might not be perfectly flat, but only nearly flat, and have a wee bit of positive curvature on average.

    As you can see, Ned Wright who was a WMAP leader, is one of the coauthors of this release of WMAP3 data:
    http://arxiv.org/abs/astro-ph/0603449
    Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
    D. N. Spergel, R. Bean, O. Dore', M. R. Nolta, C. L. Bennett, G. Hinshaw, N. Jarosik, E. Komatsu, L. Page, H. V. Peiris, L. Verde, C. Barnes, M. Halpern, R. S. Hill, A. Kogut, M. Limon, S. S. Meyer, N. Odegard, G. S. Tucker, J. L. Weiland, E. Wollack, E. L. Wright
    89 pages, 28 figures, submitted to ApJ

    "A simple cosmological model with only six parameters (matter density, Omega_m h^2, baryon density, Omega_b h^2, Hubble Constant, H_0, amplitude of fluctuations, sigma_8, optical depth, tau, and a slope for the scalar perturbation spectrum, n_s) fits not only the three year WMAP temperature and polarization data, but also small scale CMB data, light element abundances, large-scale structure observations, and the supernova luminosity/distance relationship. Using WMAP data only, the best fit values for cosmological parameters for the power-law flat LCDM model are (Omega_m h^2, Omega_b h^2, h, n_s, tau, sigma_8) = (0.127+0.007-0.013, 0.0223+0.0007-0.0009, 0.73 +- 0.03, 0.951+0.015-0.019, 0.09 +- 0.03, 0.74+0.05-0.06). The three year data dramatically shrink the allowed volume in this six-dimensional parameter space. Assuming that the primordial fluctuations are adiabatic with a power law spectrum, the WMAP data_alone_ require dark matter, and a spectral index that is significantly less than the Harrison-Zel'dovich-Peebles scale-invariant spectrum (n_s=1,r=0). Models that suppress large-scale power through a running spectral index or a large-scale cut-off in the power spectrum are a slightly better fit to the WMAP and small scale CMB data than the power-law LCDM model (Delta chi^2 = 3) The combination of WMAP and other astronomical data yields significant constraints on the geometry of the universe, the equation of state of the dark energy, the gravitational wave energy density, and neutrino properties. Consistent with the predictions of simple inflationary theories, we detect no significant deviations from Gaussianity in the CMB maps."

    look, for example, at figure 17 on page 54.
     
    Last edited: Jan 26, 2007
  5. Jan 26, 2007 #4

    marcus

    User Avatar
    Science Advisor
    Gold Member
    2015 Award
    Dearly Missed

    the idea is gaining currency that our region of spacetime was preceded by a prior collapse.
    they just had this workshop at SantaBarbara KITP called The Quantum Nature of Spacetime Singularities and it was all about removing the bang and hole singularities, by quantum models, so that evolution continues right on thru.

    If you want a sample, here is the video of Ashtekar's talk.
    http://online.kitp.ucsb.edu/online/singular_m07/ashtekar/
    also the SLIDES thumbnails are right there on the page so you can get an overview without even downloading the video of the talk

    there is a logical point---a significant distinction between spatial finite and infinte

    IF THE U IS INFINITE THEN IT MUST HAVE BEEN SOMETHING INFINITE THAT COLLAPSED

    so it would have been a whole spatially-infinite universe-----but then it would not be at all like our universe, which is slated to expand forever.

    BUT IF THE U IS FINITE then the prior collapse could merely have been a local region in a universe like ours----a black hole in other words
    ==================

    so it causes some awkwardness if one pictures the U as spatially infinite. then the bounce that Ashtekar says replaces the bang is harder to imagine (it must have been something quite different from us that collapsed)

    =================
    if one is allowed to picture the U as spatially finite then this awkwardness goes away, and it's more comfortable.

    This is why even though Ned Wright presumably has no interest in QG and bounce resolution of singularities, it still makes a difference from QG perspective when he says best fit Omega = 1.011
     
    Last edited: Jan 26, 2007
  6. Jan 27, 2007 #5

    Chronos

    User Avatar
    Science Advisor
    Gold Member
    2015 Award

    I lean towards the dead flat hypothesis, but am not convinced it is fixed. I assume we all agree the universe is intrinsically female. She occasionally teases us with a hint of curvature.
     
  7. Jan 27, 2007 #6

    hellfire

    User Avatar
    Science Advisor

    Other quantum cosmology models such as Vilenkin's tunneling proposal predict that the universe must be closed. Such a model might not be based on a solid quantum gravity theory but it might have some validity in a semiclasical approximation.
     
    Last edited: Jan 27, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Threesphere world could have come from hole ( best-fit radius 130 billion LY)
Loading...