Review on tests of General Relativity And Modified Gravity Using Pulsar Timing

Renevey, Cyril

doi:10.48550/arxiv.1905.13720

Cited by 5 publications

(9 citation statements)

References 23 publications

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“…Additional contributions to the binary's period decay may come from dipole radiation or scalarization (see e.g. [34,35,[55][56][57]). In order to quantify these effects one must specify the underlying theory considered, however in this Letter we have taken an agnostic approach.…”

Section: We Thus Neglect the Quadratic Term ġ2mentioning

confidence: 99%

Standard Sirens as a Novel Probe of Dark Energy

Wolf

Lagos

2020

Phys. Rev. Lett.

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Cosmological models with a dynamical dark energy field typically lead to a modified propagation of gravitational waves via an effectively time-varying gravitational coupling G(t). The local variation of this coupling between the time of emission and detection can be probed with standard sirens. Here we discuss the role that Lunar Laser Ranging (LLR) and binary pulsar constraints play in the prospects of constraining G(t) with standard sirens. In particular, we argue that LLR constrains the matter-matter gravitational coupling G N (t), whereas binary pulsars and standard sirens constrain the quadratic kinetic gravity self-interaction G gw (t). Generically, these two couplings could be different in alternative cosmological models, in which case LLR constraints are irrelevant for standard sirens. We use the Hulse-Taylor pulsar data and show that observations are highly insensitive to time variations of G gw (t), and we thus conclude that future gravitational waves data will become the best probe to test G gw (t), and will hence provide novel constraints on dynamical dark energy models.Introduction.-Gravitational waves (GW) are a longstanding prediction of Einstein's theory of general relativity (GR) and their recent direct detection by the LIGO/Virgo collaboration [1] has confirmed many aspects of GR [2-4] while future tests will offer exciting opportunities to probe the Universe and its constituents even further. In particular, the unknown nature of dark energy -the component driving the observed late-time accelerated expansion of the Universe [5]has motivated a number of alternative models that promote the cosmological constant of the standard ΛCDM model to be a dynamical dark energy field (see e.g. [6][7][8][9][10]). GW will provide important constraints for cosmology via standard sirens (multi-messenger detections of GW and electromagentic signals [11]), as they can test the properties of these dynamical dark energy fields as well as provide independent constraints on cosmological parameters such as the current expansion rate of the universe, H 0 , whose current observational constraints exhibit a 4-6σ tension (see review in [12]). In the upcoming years, detectors such as KAGRA [13], , the ET [15] and LISA [16] (and possible proposed detectors such as DECIGO [17]) will come online to measure GW with more precision and over cosmological distances.One notable non-trivial signature that can be probed with standard sirens is the possibility of a time-varying gravitational coupling G(t), which typically arises in dynamical dark energy models. In this case, the quadratic action for GW that propagate at the speed of light on a cosmological background is typically given by:

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Section: We Thus Neglect the Quadratic Term ġ2mentioning

confidence: 99%

Standard Sirens as a Novel Probe of Dark Energy

Wolf

Lagos

2020

Phys. Rev. Lett.

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“…This degeneracy allows us to choose a reconstructed theory with predetermined cosmological behaviour that exhibits a screening mechanism. Because of its screening property, such a theory is more likely to satisfy stringent astrophysical constraints [2,6]. We shall now develop a technique to test for, and if needed incorporate, a screening mechanism in a reconstructed theory of the form (2.21).…”

Section: Screening Reconstructed Horndeski Theoriesmentioning

confidence: 99%

“…We have now shown how to implement various screening mechanisms in Horndeski theories reconstructed from the cosmological EFT of dark energy at lowest order in the scaling parameter α. This GR limit is required in order to satisfy the numerous astrophysical constraints from Solar System tests and pulsar timing observations [2,6]. However, in order to describe corrections to the Einstein field equations we need to derive the metric field equations at next-to-leading order in α.…”

Section: Connecting Ppn and Eft Via Reconstructed Horndeski Modelsmentioning

confidence: 99%

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Parameterised post-Newtonian formalism for the effective field theory of dark energy via screened reconstructed Horndeski theories

Renevey,

Kennedy,

Lombriser

2020

Preprint

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We bring together two popular formalisms which generically parameterise deviations from General Relativity on astrophysical and cosmological scales, namely the parameterised post-Newtonian (PPN) formalism and the effective field theory (EFT) of dark energy and modified gravity. These separate formalisms are successfully applied to independently perform tests of gravity in their respective regimes of applicability on vastly different length scales. Nonlinear screening mechanisms indeed make it imperative to probe General Relativity across a wide range of scales. For a comprehensive interpretation of the complementary measurements it is important to connect them to effectively constrain the vast gravitational model space. We establish such a connection within the framework of Horndeski scalar-tensor theories restricted to a luminal propagation speed of gravitational waves. This is possible via the reconstruction of the family of linearly degenerate covariant Horndeski actions from the set of EFT functions and the subsequent derivation of the PPN parameters from the reconstructed theory. We outline the required conditions which ensure a reconstructed Horndeski model possesses a screening mechanism that enables significant modifications on cosmological scales while respecting stringent astrophysical bounds. Employing a scaling method, we then perform the general post-Newtonian expansion of the reconstructed models to derive their PPN parameters γ and β in their screened regimes.

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“…A significant parameter space of this class of models has traditionally been explored as an explanation of cosmic acceleration. Often, a significant modification of gravity on cosmological scales was invoked as the driver of cosmic acceleration, while so-called screening mechanisms would allow a recovery of GR in high-density environments or at short distances such as in galaxies or in the Solar System, where tight constraints on deviations from GR have been established [1,[27][28][29][30][31][32]. However, this concept has become severely challenged by the luminal propagation of gravitational waves (GWs) [33,34], and cosmic acceleration may be limited to the dark energy aspects of a Horndeski field rather than its direct dynamical change of gravity.…”

Section: Introductionmentioning

confidence: 99%

The effect of screening mechanisms on black hole binary inspiral waveforms

Renevey,

McManus,

Dalang

et al. 2021

Preprint

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Scalar-tensor theories leaving significant modifications of gravity at cosmological scales rely on screening mechanisms to recover General Relativity (GR) in high-density regions and pass stringent tests with astrophysical objects. Much focus has been placed on the signatures of such modifications of gravity on the propagation of gravitational waves (GWs) through cosmological distances while typically assuming their emission from fully screened regions with the wave generation strictly abiding by GR. Here, we closely analyse the impact of screening mechanisms on the inspiral GW waveforms from compact sources by employing a scaling method that enables a post-Newtonian (PN) expansion in screened regimes. Particularly, we derive the leading-order corrections to a fully screened emission to first PN order in the near zone and we also compute the modifications in the unscreened radiation zone to second PN order. For a concrete example, we apply our results to a cubic Galileon model. The resulting GW amplitude from a binary black hole inspiral deviate from its GR counterpart at most by one part in 10 2 for the modifications in the radiation zone and at most one part in 10 11 due to next-order corrections to the fully screened near zone. We expect such modifications to be undetectable by the current generation of GW detectors, but the deviation is not so small as to remain undetectable in future experiments.

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Review on tests of General Relativity And Modified Gravity Using Pulsar Timing

Cited by 5 publications

References 23 publications

Standard Sirens as a Novel Probe of Dark Energy

Standard Sirens as a Novel Probe of Dark Energy

Parameterised post-Newtonian formalism for the effective field theory of dark energy via screened reconstructed Horndeski theories

The effect of screening mechanisms on black hole binary inspiral waveforms

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