Strong Constraints on Cosmological Gravity from GW170817 and GRB 170817A

Baker, Tessa; Bellini, Emilio; Ferreira, Pedro G.; Lagos, Macarena; Noller, Johannes; Sawicki, Ignacy

doi:10.1103/physrevlett.119.251301

Cited by 786 publications

(803 citation statements)

References 78 publications

(60 reference statements)

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“…We note that the recent confirmation of the gravitational wave propagation speed to agree with the speed of light at the order of one part in quadrillionth [7,8] [30,31]. Further, the latter does not depend on φ either (except through its derivatives), hence, due to the Bianchi identities, the whole L 5 ought to vanish [32] (see also [33,34]). …”

Section: Junction Conditions Across Arbitrary Hypersurfacesmentioning

confidence: 57%

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Light-Like Shockwaves in Scalar-Tensor Theories

Racskó

Gergely

2018

Universe

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Both electromagnetic shock-waves and gravitational waves propagate with the speed of light. If they carry significant energy-momentum, this will change the properties of the space-time they propagate through. This can be described in terms of the junction conditions between space-time regions separated by a singular, null hypersurface. We derived generic junction conditions for Brans-Dicke theory in the Jordan frame, exploring a formalism based on a transverse vector, rather than normal, which can be applied to any type of hypersurfaces. In the particular case of a non-null hypersurface we obtain a generalised Lanczos equation, in which the jump of the extrinsic curvature is sourced by both the distributional energy-momentum tensor and by the jump in the transverse derivative of the scalar. In the case of null hypersurfaces, the distributional source is decomposed into surface density, current and pressure. The latter, however, ought to vanish by virtue of the scalar junction condition.

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Section: Junction Conditions Across Arbitrary Hypersurfacesmentioning

confidence: 57%

“…With φ = G −1 and J = 0 the corresponding result derived in [40] is reobtained. Finally the scalar junction Equation (32) …”

Section: The Null Casementioning

confidence: 99%

Light-Like Shockwaves in Scalar-Tensor Theories

Racskó

Gergely

2018

Universe

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“…Acknowledgements: We acknowledge the use of hi class [61] Note added: Other papers with similar conclusions appeared simultaneously to this work [44,62,63].…”

mentioning

confidence: 81%

Dark Energy After GW170817: Dead Ends and the Road Ahead

2017

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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 both signals places an exquisite bound on the GW speed |cg/c − 1| ≤ 5 · 10 −16 . 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, TeVeS and other MOND-like gravities. [6]. In this letter we present the implications that this measurement has for the nature of dark energy (DE) and tests of General Relativity (GR).The present cosmic acceleration is probably one of the greatest challenges in modern physics. Leaving the theoretical fine tuning issues aside [7], a cosmological constant is the leading candidate to explain this acceleration since it is fully consistent with observations [8]. Alternative scenarios that explain DE dynamically require either additional degrees of freedom (beyond the massless spin-2 field of GR) or a low-energy violation of fundamental principles such as locality [9]. The extremely low energy scale for DE requires additional degrees of freedom to be hidden on small scales by a screening mechanism [10], which also suppresses their rate of emission as additional gravitational wave polarizations [11].New fields coupled to gravity can affect the propagation speed of the standard GW polarizations, as measured by GW170817 and its counterparts [12]. Anomalous GW speed can be used to test even screened theories, as signals from extra-galactic sources probe unscreened, cosmological scales. In addition, effects on GW propagation accumulate over the travel time of the signals, amplifying their magnitude and yielding an impressive sensitivity. GW astronomy is therefore the most powerful tool to test models that modify GW propagation.Some of the most interesting dark energy models predict an anomalous GW speed and are ruled out by GW170817. These include cosmologically viable, screened and self-accelerating models like the covariant Galileon [13,14], or proposals to solve the cosmological constant problem like the Fab-four [15]. We will describe the implications of GW170817 on thes...

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“…The implication is in the context of cosmologically observable dark energy-induced deviations from GR: Since nextgeneration experiments are expected to only be able to constrain the α i at the O(0.1) level [18], the condition |α M + α B | 10 −2 implies that α M ∼ −α B for cosmologically significant α i . From (6), imposing this constraint within the subset of Horndeski theories (5) amounts to suppressing the cosmological effects of the G 3 cubic Horndeski interaction at the 10 −2 level [12]. In other words, as far as cosmology is concerned the relevant theory for the evolution of large scale structure to leading order now becomes…”

Section: Gw-induced Decay and Instabilitiesmentioning

confidence: 99%

Cosmological constraints on dark energy in light of gravitational wave bounds

Noller

2020

Phys. Rev. D

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Gravitational wave (GW) constraints have recently been used to significantly restrict models of dark energy and modified gravity. New bounds arising from GW decay and GW-induced dark energy instabilities are particularly powerful in this context, complementing bounds from the observed speed of GWs. We discuss the associated linear cosmology for Horndeski gravity models surviving these combined bounds and compute the corresponding cosmological parameter constraints, using CMB, redshift space distortion, matter power spectrum and BAO measurements from the Planck, SDSS/BOSS and 6dF surveys. The surviving theories are strongly constrained, tightening previous bounds on cosmological deviations from ΛCDM by over an order of magnitude. We also comment on general cosmological stability constraints and the nature of screening for the surviving theories, pointing out that a raised strong coupling scale can ensure compatibility with gravitational wave constraints, while maintaining a functional Vainshtein screening mechanism on solar system scales. Finally, we discuss the quasi-static limit as well as (constraints on) related observables for near-future surveys.

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Strong Constraints on Cosmological Gravity from GW170817 and GRB 170817A

Cited by 786 publications

References 78 publications

Light-Like Shockwaves in Scalar-Tensor Theories

Light-Like Shockwaves in Scalar-Tensor Theories

Dark Energy After GW170817: Dead Ends and the Road Ahead

Cosmological constraints on dark energy in light of gravitational wave bounds

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