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nLab > Latest Changes: Witten's Dark Fantasy

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  1.  
    • CommentRowNumber1.
    • CommentAuthorUrs
    • CommentTimeNov 15th 2019

    am finally splitting this off as a stand-alone page (material used to be at cosmological constant and at F-theory). Added a paragraph linking with inhomogeneous cosmology.

    v1, current

    • CommentRowNumber2.
    • CommentAuthorUrs
    • CommentTimeJan 9th 2020
    • (edited Jan 9th 2020)

    I have added a section References – Phenomenology and expanded the section Properties – Phenomenology, pointing out that the recent and very recent contrarian claims in astrophysics would be exactly in line with “Witten’s dark fantasy”. Heh.

    diff, v6, current

    • CommentRowNumber3.
    • CommentAuthorUrs
    • CommentTimeFeb 18th 2020
    • (edited Feb 18th 2020)

    added pointer to today’s rebuttal of the recent contrarian claim that data prefers a “closed” universe:

    • George Efstathiou, Steven Gratton, The evidence for a spatially flat Universe (arXiv:2002.06892)

    But then I also added pointer to Handley 19 and quoted their abstract as a reply to today’s critique, if you wish. Now the paragraph in total reads as follows:

    Arguments that the PLANCK satellite data actually prefers a closed spatial slices (contrary to the assumption in the current standard model of cosmology):

    A critique of these arguments is given in

    • George Efstathiou, Steven Gratton, The evidence for a spatially flat Universe (arXiv:2002.06892)

    but this critique again rests on just the combination Planck collaboration & baryon acoustic peak (BAO) & supernova-data which the above references argue cannot sensibly be combined.

    From the abstract of Handley 19:

    The curvature parameter tension between Planck 2018, cosmic microwave background lensing, and baryon acoustic oscillation data is measured using the suspiciousness statistic to be 2.5 to 3σ. Conclusions regarding the spatial curvature of the universe which stem from the combination of these data should therefore be viewed with suspicion. Without CMB lensing or BAO, Planck 2018 has a moderate preference for closed universes, with Bayesian betting odds of over 50:1 against a flat universe, and over 2000:1 against an open universe.

    diff, v9, current

    • CommentRowNumber4.
    • CommentAuthorUrs
    • CommentTimeMar 12th 2020

    added pointer to today’s

    • Eleonora Di Valentino, Alessandro Melchiorri, Joseph Silk, Cosmic Discordance: Planck and luminosity distance data exclude LCDM (arXiv:2003.04935)

    Hah!

    diff, v10, current

    • CommentRowNumber5.
    • CommentAuthorDavidRoberts
    • CommentTimeMar 12th 2020

    That’s rather remarkable. I’m liking the hypothesis of non-homogeneity more and more. Mathematically and physically, it’s very attractive, and parsimonious.

    • CommentRowNumber6.
    • CommentAuthorDavid_Corfield
    • CommentTimeMar 12th 2020

    Is the supersymmetry being rule out here

    but no finite-energy-excitation of the vacuum appears supersymmetrically, hence fermions and bosons in the model do not appear in supersymmetric spectra,

    enough to rule out MSSM?

    • CommentRowNumber7.
    • CommentAuthorUrs
    • CommentTimeMar 12th 2020
    • (edited Mar 12th 2020)

    That’s rather remarkable.

    Indeed. This will be (if it holds water) on par with the elimination of the luminiferous aether.

    enough to rule out MSSM?

    Yes, this “D=4D=4, 𝒩=1/2\mathcal{N}= 1/2 supersymmetry” is not the MSSM – or maybe you could think of this as the “MSSM with all supersymmetry completely broken, at all scales”.

    That’s the beauty of it:

    Supersymmetry is completely broken, at all scales (hence making no super-partners appear) – except on the vacuum, in that its only residual effect is to force the bosonic vacuum energy to cancel against the fermionic vacuum energy.

    That, and that it follows from Cohomotopy, of course ;-)

    • CommentRowNumber8.
    • CommentAuthorDavidRoberts
    • CommentTimeMar 12th 2020

    Supersymmetry is completely broken, at all scales (hence making no super-partners appear)

    wow, I’ve never heard of this sort of model before! Not that I dig through literature or read reviews, but one would have thought that this option would be mentioned now and then, given the current lack of experimental detection of superpartners.

    • CommentRowNumber9.
    • CommentAuthorUrs
    • CommentTimeMar 12th 2020

    I’ve never heard of this sort of model before!

    So you haven’t actually looked at the entry: Witten’s Dark Fantasy :-)

    one would have thought that this option would be mentioned now and then

    This is just one of several striking developments of modern physics out there which the dumbed-down public discourse doesn’t pick up on. The others are: b) significant detection of New Physics in the flavour sector, c) promising solution of confined QCD by holography/D-brane models. And all three solutions talk to each other. But not to the public ;-)

    • CommentRowNumber10.
    • CommentAuthorDavid_Corfield
    • CommentTimeMar 12th 2020

    Cool! I haven’t any sense of how much of a constraint it is for an 8-manifold to be an elliptic fibration. Do we know if this is a demanding condition for a Spin(7)Spin(7)-manifold?

    • CommentRowNumber11.
    • CommentAuthorUrs
    • CommentTimeMar 12th 2020

    If you want to see the detailed implementation of the Dark Fantasy in F-theory compactifications see these references ny Heckmann et al.

    • CommentRowNumber12.
    • CommentAuthorUrs
    • CommentTimeJun 10th 2024

    added pointer to today’s

    diff, v20, current

1 to 12 of 12

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