Horndeski gravity and standard sirens

Dalang, Charles; Fleury, Pierre; Lombriser, Lucas

doi:10.1103/physrevd.102.044036

Cited by 40 publications

(59 citation statements)

References 75 publications

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“…The relationship between the GW standard siren luminosity distance and the photon standard candle luminosity distance, is given by (Saltas et al 2014;Lombriser & Taylor 2016;Nishizawa 2018;Belgacem et al 2018a, b;Dalang, Fleury & Lombriser 2020),…”

Section: T H E O Rymentioning

confidence: 99%

Cosmology with the Einstein telescope: No Slip Gravity model and redshift specifications

Mitra

Mifsud

Mota

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The Einstein Telescope and other third generation interferometric detectors of gravitational waves are projected to be operational post 2030. The cosmological signatures of gravitational waves would undoubtedly shed light on any departure from the current gravitational framework. We here confront a specific modified gravity model, the No Slip Gravity model, with forecast observations of gravitational waves. We compare the predicted constraints on the dark energy equation of state parameters $w_0^{}-w_a^{}$, between the modified gravity model and that of Einstein gravity. We show that the No Slip Gravity model mimics closely the constraints from the standard gravitational theory, and that the cosmological constraints are very similar. The use of spectroscopic redshifts, especially in the low–redshift regime, lead to significant improvements in the inferred parameter constraints. We test how well such a prospective gravitational wave dataset would function at testing such models, and find that there are significant degeneracies between the modified gravity model parameters, and the cosmological parameters that determine the distance, due to the gravitational wave dimming effect of the modified theory.

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Section: T H E O Rymentioning

confidence: 99%

Cosmology with the Einstein telescope: No Slip Gravity model and redshift specifications

Mitra

Mifsud

Mota

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…As the third generation (3G) detectors, such as the space-based ones, LISA [18], TianQin [19], Taiji [20], DECIGO [21], and the ground-based ones, ET [50] and CE [51], are able to detect GWs emitted from such sources as far as at the redshift z 100 [52], it is very important and timely to carry out such studies systematically. Such studies were already initiated some years ago [57,59,60] in the framework of Einstein's theory, and more recently in scalar-tensor theories [61][62][63][64]64].…”

Section: Discussionmentioning

confidence: 99%

“…Lately, such studies have been further generalized to scalar-tensor theories [61], including Horndeski [62][63][64] and SMG [64] theories.…”

Section: Introductionmentioning

confidence: 99%

Gravitational wave cosmology I: high frequency approximation

Fier,

Fang,

et al. 2021

Preprint

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In this paper, we systematically study gravitational waves (GWs) first produced by remote compact astrophysical sources and then propagating in our inhomogeneous universe through cosmic distances, before arriving at detectors. To describe such GWs properly, we introduce three scales, λ, Lc and L, denoting, respectively, the typical wavelength of GWs, the scale of the cosmological perturbations, and the size of the observable universe. For GWs to be detected by the current and foreseeable detectors, the condition λ Lc L holds. Then, such GWs can be approximated as high-frequency GWs and be well separated from the background γµν by averaging the spacetime curvatures over a scale , where λ Lc, and gµν = γµν + hµν with ≡ λ/L, and hµν denotes the GWs. In order for the backreaction of the GWs to the background spacetimes to be negligible, we must assume that |hµν | 1, in addition to the condition 1, which are also the conditions for the linearized Einstein field equations for hµν to be valid. Such studies can be significantly simplified by properly choosing gauges, such as the spatial (χ0µ = 0), traceless (γ µν χµν = 0), and Lorentz (∇ ν χµν = 0) gauges, where χµν ≡ hµν − hγµν /2, and ∇ ν denotes the covariant derivative with respect to γµν . We show that these three different gauge conditions can be imposed simultaneously, even when the background is not vacuum, as long as the high-frequency GW approximation is valid. However, to develop the formulas that can be applicable to as many cases as possible, in this paper we first write down explicitly the linearized Einstein field equations for χµν by imposing only the spatial gauge. Then, applying these formulas together with the geometrical optics approximation to such GWs, we find that they still move along null geodesics and its polarization bi-vector is parallel-transported, even when both the cosmological scalar and tensor perturbations are present. In addition, we also calculate the gravitational integrated Sachs-Wolfe effects due to these two kinds of perturbations, whereby the dependences of the amplitude, phase and luminosity distance of the GWs on these perturbations are read out explicitly.

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“…One of the delicate issues in studying GW propagation in modified gravity is to distinguish tensor from scalar fluctuations, and correctly identify their roles in the evolution equations of high-frequency fields. This topic started with the classic papers [52,53], and has been recently reconsidered in [54][55][56][57][58] using a variety of methods. The issue can be subtle in theories where scalar and metric fluctuations propagate with different speed, a phenomenon associated with spontaneous breaking of global Lorentz invariance by means of a non-vanishing time-like gradient for the dark energy field.…”

Section: Jcap06(2021)050 2 Our Set-upmentioning

confidence: 99%

Gravitational-wave cosmological distances in scalar-tensor theories of gravity

Tasinato

Garoffolo

Bertacca

et al. 2021

J. Cosmol. Astropart. Phys.

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We analyze the propagation of high-frequency gravitational waves (GW) in scalartensor theories of gravity, with the aim of examining properties of cosmological distances as inferred from GW measurements. By using symmetry principles, we first determine the most general structure of the GW linearized equations and of the GW energy momentum tensor, assuming that GW move with the speed of light. Modified gravity effects are encoded in a small number of parameters, and we study the conditions for ensuring graviton number conservation in our covariant set-up. We then apply our general findings to the case of GW propagating through a perturbed cosmological space-time, deriving the expressions for the GW luminosity distance d (GW) L and the GW angular distance d (GW) A. We prove for the first time the validity of Etherington reciprocity law dfor a perturbed universe within a scalar-tensor framework. We find that besides the GW luminosity distance, also the GW angular distance can be modified with respect to General Relativity. We discuss implications of this result for gravitational lensing, focussing on time-delays of lensed GW and lensed photons emitted simultaneously during a multimessenger event. We explicitly show how modified gravity effects compensate between different coefficients in the GW time-delay formula: lensed GW arrive at the same time as their lensed electromagnetic counterparts, in agreement with causality constraints.

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Horndeski gravity and standard sirens

Cited by 40 publications

References 75 publications

Cosmology with the Einstein telescope: No Slip Gravity model and redshift specifications

Cosmology with the Einstein telescope: No Slip Gravity model and redshift specifications

Gravitational wave cosmology I: high frequency approximation

Gravitational-wave cosmological distances in scalar-tensor theories of gravity

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