Revival of the Deser-Woodard nonlocal gravity model: Comparison of the original nonlocal form and a localized formulation

Park, Sohyun

doi:10.1103/physrevd.97.044006

Cited by 26 publications

(29 citation statements)

References 123 publications

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“…The same result can be found by writing the Poisson equation for the perturbations around FRW in the large-k limit, which gives [19,20]…”

Section: Dw Modelsupporting

confidence: 64%

“…To this purpose we consider the equation 2S = −U , that, in the same approximations become The term δU here must be dropped, since we found that δU 2Φ and we have already dropped the terms O(Φ) from the wave operator. 20 As for the term 4ΦṠ c , we can estimate its typical value as follows. The time evolution of Φ is determined by the typical time-scale T of the evolving matter structures,Φ ∼ Φ/T , while the cosmological background solution evolves with a time-scale given by H,Ṡ c ∼ HS c .…”

Section: A Static Solution For the Rr Modelmentioning

confidence: 99%

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Testing nonlocal gravity with Lunar Laser Ranging

Belgacem

Finke

Frassino

et al. 2019

J. Cosmol. Astropart. Phys.

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We study the impact of the limit on |Ġ|/G from Lunar Laser Ranging on "nonlocal gravity", i.e. on models of the quantum effective action of gravity that include nonlocal terms relevant in the infrared, such as the "RR" and "RT" models proposed by our group, and the Deser-Woodard (DW) model. We elaborate on the analysis of Barreira et al.[1] and we confirm their findings that (under plausible assumptions such as the absence of strong backreaction from non-linear structures), the RR model is ruled out. We also show that the mechanism of "perfect screening for free" suggested for the DW model actually does not work and the DW model is also ruled out. In contrast, the RT model passes all phenomenological consistency tests and is still a viable candidate.

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“…The same result can be found by writing the Poisson equation for the perturbations around FRW in the large-k limit, which gives [19,20]…”

Section: Dw Modelsupporting

confidence: 64%

Section: A Static Solution For the Rr Modelmentioning

confidence: 99%

Testing nonlocal gravity with Lunar Laser Ranging

Belgacem

Finke

Frassino

et al. 2019

J. Cosmol. Astropart. Phys.

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“…* tshuxun@whu.edu.cn should be mentioned here, the Deser-Woodard nonlocal gravity could suppress the growth rate of a large scale structure formation [14,15], which is in better agreement with observations, and this good property may be related to the fact that Ψ = Φ in the Deser-Woodard theory. If we require Ψ = Φ, we may lose this merit.…”

supporting

confidence: 80%

Scalar-tensor nonlocal gravity

Tian

2018

Phys. Rev. D

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In order to explain the late-time cosmological acceleration, we propose a new pure geometric gravity based on Deser-Woodard theory [Phys. Rev. Lett. 99, 111301 (2007)], in which the expansion of a matter-dominated universe can be accelerating. This new theory behaves as well as general relativity in solar system and gravitational waves, which is an important improvement over Deser-Woodard nonlocal gravity. Especially, for the simplest case, theoretical considerations determine all the parameters that appear in the Lagrangian. I. INTRODUCTIONWhich theory is the most beautiful one to explain the late-time cosmological acceleration? Dark energy, e.g., quintessence [1] or phantom [2], is a simple model. However, this mysterious matter is undetectable in the local gravitational systems, and thus, its existence lacks direct verification. Modified gravity is also a good candidate (see [3][4][5][6] for reviews). One can couple new fields to the Einstein-Hilbert Lagrangian or add higher-order geometric terms to the action. But current mainstream modified gravities are not good enough to replace Einstein's theory. The problems come from observations and aesthetics. Many simple models, e.g., f (R) = R + αR 2 theory, can be directly ruled out by observations [5]. In order to fit all known observations, one has to construct complex structures for the Lagrangian, e.g., the Hu-Sawicki model [7]. This always makes the theory not so charming, even though it fits the data well. Another aesthetics problem is that, in order to explain the late-time acceleration, classical theories generally need a parameter related to the Hubble constant H 0 . This may be a potential factor that makes theories suffer from the coincidence problem. We believe if a pure geometric gravity does not introduce any H 0 -related parameters into the Lagrangian and can behave well in various gravitational applications, then it is comparable to previous theories.Pure fourth-order gravity [8] seems to be a good choice. However, combined with Eq. (8) and Eq. (27) in [8] and ρ 0 = O(H 2 0 /G) from dimensional analysis, we obtain σ i = O(c/H 0 ), which is inconsistent with the explanation of [8] that σ i is the size of fundamental particles. Deser-Woodard nonlocal gravity [9] is a pure geometric theory and only introduces dimensionless parameters in the Lagrangian. This theory could explain the late-time acceleration, but gives Ψ = Φ in the weak field limit [see metric (4) for the meaning of Φ and Ψ] for the general formalism [10]. The Cassini mission gives Ψ/Φ = 1 + (2.1 ± 2.3) × 10 −5 in the Solar system [11], and recently, Ψ = Φ has been confirmed at the Galaxy scale [12]. We believe a good gravity theory should give Ψ that exactly equals, not close, to Φ [13]. One thing

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“…This feature resembles such well-known approach as nonlocal modifications of gravity, see e.g. [14,15,16,17,18] and references therein. There is rather popular viewpoint that nonlocal gravity theories are of importance for solving basic problems of cosmology -that of dark energy and dark matter.…”

Section: Discussion and Concluding Remarkssupporting

confidence: 56%

Galaxy Rotation Curves in the µ-Deformation Based Approach to Dark Matter

2019

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We elaborate further the µ-deformation-based approach to modeling dark matter, in addition to the earlier proposed use of µ-deformed thermodynamics. Herein, we construct µdeformed analogs of the Lane-Emden equation (for density profiles), and find their solutions. Using these, we plot the rotation curves for a number of galaxies. Different curves describing chosen galaxies are labeled by respective (differing) values of the deformation parameter µ. As result, the use of µ-deformation leads to improved agreement with observational data. For all the considered galaxies, the obtained rotation curves (labeled by µ) agree better with data, as compared to the well known Bose-Einstein condensate model results of T. Harko. Besides, for five of the eight cases of galaxies we find better picture for rotation curves than the corresponding Navarro-Frenk-White (NFW) curves. Possible physical meaning of the parameter µ, basic for this version of µ-deformation, is briefly discussed.

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Revival of the Deser-Woodard nonlocal gravity model: Comparison of the original nonlocal form and a localized formulation

Cited by 26 publications

References 123 publications

Testing nonlocal gravity with Lunar Laser Ranging

Testing nonlocal gravity with Lunar Laser Ranging

Scalar-tensor nonlocal gravity

Galaxy Rotation Curves in the µ-Deformation Based Approach to Dark Matter

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