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A Atoms Of Space, Gravity and the Cosmological Constant

  1. Mar 29, 2016 #1

    marcus

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    This Invited Review article just came out:
    http://arxiv.org/abs/1603.08658
    The Atoms Of Space, Gravity and the Cosmological Constant
    T. Padmanabhan
    (Submitted on 29 Mar 2016)
    I describe an approach which connects classical gravity with the quantum microstructure of spacetime. The field equations arise from maximizing the density of states of matter plus geometry. The former is identified using the thermodynamics of null surfaces while the latter arises due to the existence of a zero-point length in the spacetime. The resulting field equations remain invariant when a constant is added to the matter Lagrangian, which is a symmetry of the matter sector. Therefore, the cosmological constant arises as an integration constant. A non-zero value Λ of the cosmological constant renders the amount of cosmic information (Ic) accessible to an eternal observer finite and hence is directly related to it. This relation allows us to determine the numerical value of Λ from the quantum structure of spacetime.
    Invited Review; 32 pages; 3 figures

    ==quote==
    Substituting this into Eq. (59), we get a remarkable formula for the cosmological constant
    ...
    ...
    If we take the typical values ρin = (1.2 × 1015 GeV)4 , ρeq = (0.86 eV)4 , we get ρΛ = (2.2 × 10−3 eV)4 which agrees well with observed value! In other words, the idea that the cosmic information content accessible to an eternal observer, Ic, is equal to the basic quantum gravitational unit of information IQG = 4π, determines the numerical value of the cosmological constant correctly. ...
    ==endquote==
     
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  3. Mar 29, 2016 #2

    marcus

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    I see that these days people not infrequently present models where the value of the cosmological constant Λ is determined NOT by anything like a matter field "vacuum energy" but rather from some feature of microscopic quantum spacetime geometry.
    IOW it is an intrinsic feature of quantum geometry itself---the "atoms of geometry".

    It seems to be getting researchers' attention, and they have various ideas about it. This is one. Thanu ("Paddy") Padmanabhan is prominent theoretician.
    http://inspirehep.net/author/profile/T.Padmanabhan.1
    Number of papers analyzed: 267
    Number of citations: 12966
    Citations per paper (average): 48.6
    Breakdown of papers by times cited:
    Renowned papers (500+) 2
    Famous papers (250-499) 7
    Very well-known papers (100-249) 19
    Well-known papers (50-99) 26
    Known papers (10-49) 111
    Less known papers (1-9) 76

    I can only assume this one will contribute to the growing researcher interest in this kind of explanation of the cosmological constant.
    which incidentally is easiest to grasp as an asymptotic or baseline percentage distance growth rate.
    Currently measured at 1/173 of one percent per million years.
     
    Last edited: Mar 29, 2016
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