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A Falsifications and constraints due to GW measurements

  1. Oct 22, 2017 #1
    This thread is to serve as
    - a collection of theories that have been falsified by and/or have had new constrained placed on them by the ongoing gravitational wave measurements.
    - a place to discuss the further constraining/falsifying of still existing models using GW data.

    I'll start by posting a few papers offering falsifications and/or new constraints:
    Boran et al. 2017, GW170817 Falsifies Dark Matter Emulators
    Baker et al. 2017, Strong constraints on cosmological gravity from GW170817 and GRB 170817A
    Di Valentino et al. 2017, Cosmological constraints combining Planck with the recent gravitational-wave standard siren measurement of the Hubble constant
    Margalit et al. 2017, Constraining the Maximum Mass of Neutron Stars From Multi-Messenger Observations of GW170817
    Ezquiaga et al. 2017, Dark Energy after GW170817 (1)
    Sakstein et al. 2017, Implications of the Neutron Star Merger GW170817 for Cosmological Scalar-Tensor Theories
    Creminelli at al. 2017, Dark Energy after GW170817 (2)
    Wang et al. 2017, GW170817/GRB 170817A/AT2017gfo association: some implications for physics and astrophysics
     
  2. jcsd
  3. Oct 27, 2017 #2

    mfb

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    A nice collection.

    I wonder how constraints on GR alternatives will change with future observations. Improving the time correlation between GW and electromagnetic signal by a small factor shouldn't make a big difference. We can get more independent estimates of the Hubble constant, of course, but that is a different topic.
     
  4. Nov 8, 2017 #3
    If one could observe more of this sort of event, one could get some idea of the time from the G-wave signal to the gamma-ray one. One may then look for how it varies with distance, or more precisely, estimated Shapiro gravitational time delay from nearby galaxies. The error in the time-delay estimate will go as 1/sqrt(N) for N events, meaning that it may take a lot of events to improve very much on this result.

    Also, it's an interesting term for G-wave events: "standard siren". Presumably because "standard candle" is not a good fit.
     
  5. Dec 23, 2017 #4

    General Relativity rules!


    Reining in Alternative Gravity


    https://physics.aps.org/articles/v10/134#c5

    ----

    Dark Energy After GW170817: Dead Ends and the Road Ahead

    https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.251304

    We use this result to probe the nature of dark energy (DE), showing that a large class of scalar-tensor theories and DE models are highly disfavored. As an example we consider the covariant Galileon, a cosmologically viable, well motivated gravity theory which predicts a variable GW speed at low redshift. Our results eliminate any late-universe application of these models, as well as their Horndeski and most of their beyond Horndeski generalizations. Three alternatives (and their combinations) emerge as the only possible scalar-tensor DE models: (1) restricting Horndeski’s action to its simplest terms, (2) applying a conformal transformation which preserves the causal structure, and (3) compensating the different terms that modify the GW speed (to be robust, the compensation has to be independent on the background on which GWs propagate). Our conclusions extend to any other gravity theory predicting varying cg such as Einstein-Aether, Hořava gravity, Generalized Proca, tensor-vector-scalar gravity (TEVES), and other MOND-like gravities.


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    Last edited by a moderator: Dec 23, 2017
  6. Dec 24, 2017 #5

    strangerep

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    ArXiv version here.
     
  7. Dec 28, 2017 #6

    Chronos

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    I am inclined to interpret all these as merely slightly different ways of reaching the same core conclusion: empty 'space' has no measurable affect upon the propagation speed of gravitational or electromagnetic waves. Sounds suspiciously similar to the conclusion reached by Einstein.
     
  8. Dec 29, 2017 #7
    .

    Bounding the Speed of Gravity with Gravitational Wave Observations
    https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.161102

    The time delay between gravitational wave signals arriving at widely separated detectors can be used to place upper and lower bounds on the speed of gravitational wave propagation. Using a Bayesian approach that combines the first three gravitational wave detections reported by the LIGO Scientific and Virgo Collaborations we constrain the gravitational waves propagation speed cgw to the 90% credible interval 0.55c<cgw<1.42c, where c is the speed of light in vacuum. These bounds will improve as more detections are made and as more detectors join the worldwide network. Of order 20 detections by the two LIGO detectors will constrain the speed of gravity to within 20% of the speed of light, while just five detections by the LIGO-Virgo-Kagra network will constrain the speed of gravity to within 1% of the speed of light.

    .
     
  9. Jan 12, 2018 #8

    ohwilleke

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    Not sure if this is on topic or not, although it is certainly related to some extent.

    Indications of an unexpected signal associated with the GW170817 binary neutron star inspiral
    E. Fischbach, V. E. Barnes, N. Cinko, J. Heim, H. B. Kaplan, D. E. Krause, J. R. Leeman, S. A. Mathews, M. J. Mueterthies, D. Neff, M. Pattermann
    (Submitted on 10 Jan 2018)
    We report experimental evidence at the 2.5σ level for an unexpected signal associated with the GW170817 binary neutron star inspiral. This evidence derives from a laboratory experiment simultaneously measuring the β-decay rates of Si-32 and Cl-36 in a common detector. Whereas the Si-32 and Cl-36 decay rates show no statistical correlation before or after the inspiral, they are highly correlated (∼95%) in the 5 hour time interval immediately following the inspiral. If we interpret this correlation as arising from the influence of particles emitted during the inspiral, then we can estimate the mass mx of these particles from the time delay between the gravity-wave signal and a peak in the β-decay data. We find for particles of energy 10 MeV, mx ≲ 16 eV which includes the neutrino mass region mν ≲ 2 eV. The latter is based on existing limits for the masses mi of the three known neutrino flavors. Additionally, we find that the correlation is even stronger if we include data in the 80 minute period before the arrival of the gravity wave signal. Given the large number of radionuclides whose decays are being monitored at any given time, we conjecture that other groups may also be in a position to search for statistically suggestive fluctuations of radionuclide decay rates associated with the GW170817 inspiral.
     
  10. Jan 12, 2018 #9

    mfb

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    ... we should expect a 2.5 sigma deviation somewhere every day.

    Needless to mention that the neutrino detectors didn't pick up anything.
     
  11. Jan 13, 2018 #10

    Vanadium 50

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    Fischbach has a track record of finding dramatic new physics effects in other people's data - effects that subsequently are shown not to exist.
     
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