This thread is to serve as(adsbygoogle = window.adsbygoogle || []).push({});

- 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 Abstract said:On August 17, 2017 the LIGO interferometers detected the gravitational wave (GW) signal (GW170817) from the coalescence of binary neutron stars. This signal was also simultaneously seen throughout the electromagnetic (EM) spectrum from radio waves to gamma-rays. We point out that this simultaneous detection of GW and EM signals rules out a class of modified gravity theories, which dispense with the need for dark matter. This simultaneous observation also provides the first ever test of Einstein's Weak Equivalence Principle (WEP) between gravitons and photons. We calculate the Shapiro time delay due to the gravitational potential of the total dark matter distribution along the line of sight (complementary to the calculation in arXiv:1710.05834) to be about 1000 days. Using this estimate for the Shapiro delay and from the time difference of 1.7 seconds between the GW signal and gamma-rays, we can constrain violations of WEP using the parameterized post-Newtonian (PPN) parameter γ, and is given by |γGW−γEM|<3.9×10−8.

Di Valentino et al. 2017, Cosmological constraints combining Planck with the recent gravitational-wave standard siren measurement of the Hubble constant Abstract said:The detection of an electromagnetic counterpart (GRB 170817A) to the gravitational wave signal (GW170817) from the merger of two neutron stars opens a completely new arena for testing theories of gravity. We show that this measurement allows us to place stringent constraints on general scalar-tensor and vector-tensor theories, while allowing us to place an independent bound on the graviton mass in bimetric theories of gravity. These constraints severely reduce the viable range of cosmological models that have been proposed as alternatives to general relativistic cosmology.

Margalit et al. 2017, Constraining the Maximum Mass of Neutron Stars From Multi-Messenger Observations of GW170817 Abstract said:The recent observations of gravitational-wave and electromagnetic emission produced by the merger of the binary neutron-star system GW170817 have opened the possibility of using standard siren to constrain the value of the Hubble constant. While the reported bound is significantly weaker than those recently derived by usual luminosity distances methods, they do not require any form of cosmic distance ladder and can be considered as complementary and, in principle, more conservative. Here we combine the new measurement with the Planck Cosmic Microwave Background observations in a 12 parameters extended LambdaCDM scenario, where the Hubble constant is weakly constrained by CMB data and bound to a low value H0=55+7−20 km/s/Mpc at 68 % C.L. The non-Gaussian shape of the GW170817 bound makes lower values of the Hubble constant in worst agreement with observations. The inclusion of the new GW170817 Hubble constant measurement significantly reduces the allowed parameter space, improving the cosmological bounds on several parameters as the neutrino mass, curvature and the dark energy equation of state.

Ezquiaga et al. 2017, Dark Energy after GW170817 (1) Abstract said:We combine electromagnetic (EM) and gravitational wave (GW) information on the binary neutron star (NS) merger GW170817 in order to constrain the radii Rns and maximum mass Mmax of NSs. GW170817 was followed by a range of EM counterparts, including a weak gamma-ray burst (GRB), kilonova (KN) emission from the radioactive decay of the merger ejecta, and X-ray/radio emission consistent with being the synchrotron afterglow of a more powerful off-axis jet. The type of compact remnant produced in the immediate merger aftermath, and its predicted EM signal, depend sensitively on the high-density NS equation of state (EOS). For a soft EOS which supports a low Mmax, the merger undergoes a prompt collapse accompanied by a small quantity of shock-heated or disk wind ejecta, inconsistent with the large quantity ≳10−2M⊙ of lanthanide-free ejecta inferred from the KN. On the other hand, if Mmax is sufficiently large, then the merger product is a rapidly-rotating supramassive NS (SMNS), which must spin-down before collapsing into a black hole. A fraction of the enormous rotational energy necessarily released by the SMNS during this process is transferred to the ejecta, either into the GRB jet (energy EGRB) or the KN ejecta (energy Eej), also inconsistent with observations. By combining the total binary mass of GW170817 inferred from the GW signal with conservative upper limits on EGRB and Eej from EM observations, we constrain the likelihood probability of a wide-range of previously-allowed EOS. These two constraints delineate an allowed region of the Mmax−Rns parameter space, which once marginalized over NS radius places an upper limit of Mmax≲2.17M⊙ (90\%), which is tighter or arguably less model-dependent than other current constraints.

Sakstein et al. 2017, Implications of the Neutron Star Merger GW170817 for Cosmological Scalar-Tensor Theories Abstract said:Multi-messenger gravitational wave (GW) astronomy has commenced with the detection of the binary neutron star merger GW170817 and its associated electromagnetic counterparts. The almost coincident observation of the GW and the gamma ray burst GRB170817A constrain the speed of GWs at the level of |cg/c−1|≤4.5⋅10−16. We use this result to probe the nature of dark energy (DE), showing that scalar-tensor theories with derivative interactions with the curvature are highly disfavored. As an example we consider the case of Galileons, a well motivated gravity theory with viable cosmology, which predicts a variable GW speed at low redshift, and is hence strongly ruled out by GW170817. Our result essentially eliminates any cosmological application of these DE models and, in general, of quartic and quintic Horndeski and most beyond Horndeski theories. We identify the surviving scalar-tensor models and, in particular, present specific beyond Horndeski theories avoiding this constraint. The viable scenarios are either conformally equivalent to theories in which cg=c or rely on cancellations of the anomalous GW speed that are valid on arbitrary backgrounds. Our conclusions can be extended to any other gravity theory predicting an anomalous GW propagation speed such as Einstein-Aether, Ho\v{r}ava gravity, Generalized Proca, TeVeS and other MOND-like gravities.

Creminelli at al. 2017, Dark Energy after GW170817 (2) Abstract said:The LIGO/VIRGO collaboration has recently announced the detection of gravitational waves from a neutron star-neutron star merger (GW170817) and the simultaneous measurement of an optical counterpart (the gamma-ray burst GRB 170817A). The close arrival time of the gravitational and electromagnetic waves limits the difference in speed of photons and gravitons to be less than about one part in 1015. This has three important implications for cosmological scalar-tensor gravity theories that are often touted as dark energy candidates and alternatives to ΛCDM. First, for the most general scalar-tensor theories---beyond Horndeski models---three of the five parameters appearing in the effective theory of dark energy can now be severely constrained on astrophysical scales; we present the results of combining the new gravity wave results with galaxy cluster observations. Second, the combination with the lack of strong equivalence principle violations exhibited by the supermassive black hole in M87, constrains the quartic galileon model to be cosmologically irrelevant. Finally, we derive a new bound on the disformal coupling to photons that implies that such couplings are irrelevant for the cosmic evolution of the field.

Wang et al. 2017, GW170817/GRB 170817A/AT2017gfo association: some implications for physics and astrophysics Abstract said:The observation of GW170817 and its electromagnatic counterpart implies that gravitational waves travel at the speed of light, with deviations smaller than a few parts in 10−15. We discuss the consequences of this experimental result for models of dark energy and modified gravity characterized by a single scalar degree of freedom. To avoid tuning, the speed of gravitational waves must be unaffected not only for our particular cosmological solution, but also for nearby solutions obtained by slightly changing the matter abundance. For this to happen the coefficients of various operators must satisfy precise relations that we discuss both in the language of the Effective Field Theory of Dark Energy and in the covariant one, for Horndeski, beyond Horndeski and degenerate higher-order theories. The simplification is dramatic: of the three functions describing quartic and quintic beyond Horndeski theories, only one remains and reduces to a standard conformal coupling to the Ricci scalar for Horndeski theories. We show that the deduced relations among operators do not introduce further tuning of the models, since they are stable under quantum corrections.

Abstract said:On 17 August 2017, a gravitational wave event (GW170817) and an associated short gamma-ray burst (GRB 170817A) from a binary neutron star merger had been detected. The followup optical/infrared observations also identified the macronova/kilonova emission (AT2017gfo). In this work we discuss some implications of the remarkable GW170817/GRB 170817A/AT2017gfo association. We show that the ∼1.7s time delay between the gravitational wave (GW) and GRB signals imposes very tight constraint on the superluminal movement of gravitational waves (i.e., the relative departure of GW velocity from the speed of light is ≤4.3×10−16) or the possible violation of weak equivalence principle (i.e., the difference of the gamma-ray and GW trajectories in the gravitational field of the galaxy and the local universe should be within a factor of ∼3.4×10−9). The so-called Dark Matter Emulators and a class of contender models for cosmic acceleration ("Covariant Galileon") are ruled out, too. The successful identification of Lanthanide elements in the macronova/kilonova spectrum also excludes the possibility that the progenitors of GRB 170817A are a binary strange star system. The high neutron star merger rate (inferred from both the local sGRB data and the gravitational wave data) together with the significant ejected mass strongly suggest that such mergers are the prime sites of heavy r-process nucleosynthesis.

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# A Falsifications and constraints due to GW measurements

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