Nonlocal gravity. Conceptual aspects and cosmological predictions

Belgacem, Enis; Dirian, Yves; Foffa, Stefano; Maggiore, Michele

doi:10.1088/1475-7516/2018/03/002

Cited by 169 publications

(241 citation statements)

References 174 publications

(394 reference statements)

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“…theories where the quantum effective action, not the classical one, is non-local) are necessarily acausal [63]. However, this argument does not apply in our case because the non-localities we deal with do not need any prescription for the −1 factor, as it always appears in a combination γ( ) = c 0 + c 1 + O( 2 ) which is analytic when " = 0" (in particular, γ r * ( ) = −r * + (r 2 * /2) + O( 3 )).…”

Section: Jhep05(2018)087mentioning

confidence: 99%

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Initial conditions and degrees of freedom of non-local gravity

Calcagni

Modesto

Nardelli

2018

J. High Energ. Phys.

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Abstract:We prove the equivalence between non-local gravity with an arbitrary form factor and a non-local gravitational system with an extra rank-2 symmetric tensor. Thanks to this reformulation, we use the diffusion-equation method to transform the dynamics of renormalizable non-local gravity with exponential operators into a higher-dimensional system local in spacetime coordinates. This method, first illustrated with a scalar field theory and then applied to gravity, allows one to solve the Cauchy problem and count the number of initial conditions and of non-perturbative degrees of freedom, which is finite. In particular, the non-local scalar and gravitational theories with exponential operators are both characterized by four initial conditions in any dimension and, respectively, by one and eight degrees of freedom in four dimensions. The fully covariant equations of motion are written in a form convenient to find analytic non-perturbative solutions.

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Section: Jhep05(2018)087mentioning

confidence: 99%

“…This interesting possibility will be explored elsewhere. 6 In the −1 case, the regularization procedure needed to define 1/k 2 as a tempered distribution prevents the Green function to be symmetric under the exchange x ↔ y, leading to the known mismatch between causality and symmetry of the propagator [63].…”

Section: Jhep05(2018)087mentioning

confidence: 99%

Initial conditions and degrees of freedom of non-local gravity

Calcagni

Modesto

Nardelli

2018

J. High Energ. Phys.

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“…(2. 23) The fact that this expression for h TT µν is indeed transverse and traceless is easily checked by using the properties of P µν , ∂ µ P µν = 0, η µν P ρ µ P σ ν = P ρσ and η µν P µν = 3. Plugging the decomposition (2.19) into the action (2.16) one finds that µ cancels (an obvious consequence of the fact that it is a pure gauge mode), and [13] S (2)…”

Section: )mentioning

confidence: 92%

“…(2.68) below. These issues have been reviewed at length in [22,23] (see also [24][25][26][27]). Here, for completeness, we summarize them briefly.…”

Section: Aspects Of Effective Nonlocal Theoriesmentioning

confidence: 99%

“…We focus on the RT model, that eventually turns out to be the most interesting phenomenologically. In order to make the paper self-contained, we begin by reviewing material on the background evolution already discussed and reviewed in [20,22,23,84]. We will then move to a detailed discussion of the perturbations and an updated comparison with the cosmological data.…”

Section: Phenomenology Of the Rt Modelmentioning

confidence: 99%

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Gravity in the infrared and effective nonlocal models

Belgacem

Dirian

Finke

et al. 2020

J. Cosmol. Astropart. Phys.

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We provide a systematic and updated discussion of a research line carried out by our group over the last few years, in which gravity is modified at cosmological distances by the introduction of nonlocal terms, assumed to emerge at an effective level from the infrared behavior of the quantum theory. The requirement of producing a viable cosmology turns out to be very stringent and basically selects a unique model, in which the nonlocal term describes an effective mass for the conformal mode. We discuss how such a specific structure could emerge from a fundamental local theory of gravity, and we perform a detailed comparison of this model with the most recent cosmological datasets, confirming that it fits current data at the same level as ΛCDM.Most notably, the model has striking predictions in the sector of tensor perturbations, leading to a very large effect in the propagation of gravitational wave (GWs) over cosmological distances. At the redshifts relevant for the next generation of GW detectors such as Einstein Telescope, Cosmic Explorer and LISA, this leads to deviations from GR that could be as large as 80%, and could be verified with the detection of just a single coalescing binary with electromagnetic counterpart. This would also have potentially important consequences for the search of the counterpart since, for a given luminosity distance to the source, as inferred through the GW signal, the actual source redshift could be significantly different from that predicted by ΛCDM. At the redshifts relevant for advanced LIGO/Virgo/Kagra the effect is smaller, but still potentially observable over a few years of runs at target sensitivity. arXiv:2001.07619v1 [astro-ph.CO] 21 Jan 2020 4 Conclusions 66 A Difficulties of alternative nonlocal models 68 -1 -2 The Lichnerowicz operator is defined by E µν,ρσ ≡ 1 2, where 2 = η µν ∂µ∂ν is the flat-space d'Alembertian. We use the signature ηµν = (−, +, +, +) and MTW [14] sign conventions. 3 We assume here 3 + 1 spacetime dimensions. See [13] for the corresponding equations in d + 1 spacetime dimensions, with d generic.

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Quantum‐Gravitational Trans‐Planckian Radiation by a Rotating Black Hole

Nurmagambetov

Park

2021

Fortschritte der Physik

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We recently studied the energy behavior of a quantum‐corrected time‐dependent black hole. The system analyzed was a quantum‐corrected Kerr solution that settles down to a stationary configuration as the time dependence fades out. A trans‐Planckian energy scaling in the vicinity of the event horizon resulted, and we proposed the trans‐Planckian radiation to be the missing link in the glowing mechanism of active galactic nuclei. The main goal of the present work is to examine the scaling and structure of the radiation by analyzing the quantum momentum density. We again observe a trans‐Planckian behavior. Furthermore, the momentum density displays structures that are indicative of a disk‐like configuration near the equator and a collimated outflow of matter from the poles. The bipolar outflow (disk‐like structure) should be an essential part of the underlying mechanism for jets (accretion disks) of active galactic nuclei.

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Nonlocal gravity. Conceptual aspects and cosmological predictions

Abstract: 3.3.6 Speed and propagation of gravitational waves 42 4 Conclusions 46 A The ∆ 4 model 47 e iΓ[gµν ] = e iS EH [gµν ] Dϕ e iSm[gµν ;ϕ] ≡ e iS EH [gµν ] e iΓm[gµν ] . (2.7)

Cited by 169 publications

References 174 publications

Initial conditions and degrees of freedom of non-local gravity

Initial conditions and degrees of freedom of non-local gravity

Gravity in the infrared and effective nonlocal models

Quantum‐Gravitational Trans‐Planckian Radiation by a Rotating Black Hole

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