Generalized ghost-free propagators in nonlocal field theories

Buoninfante, Luca; Lambiase, Gaetano; Miyashita, Yuichi; Takebe, Wataru; Yamaguchi, Masahide

doi:10.1103/physrevd.101.084019

Cited by 47 publications

(33 citation statements)

References 184 publications

(193 reference statements)

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“…This guaranties the powercounting renormalizability and raises the hope that Black-Hole and Big Bang singularities are being resolved in gravity theories of this kind. A number of crucial questions has been investigated recently regarding the resolution of singularities [23,[43][44][45][46][47][48][49][50][51][52][53][54][55] in this approach. The arguments above explain why such an infinite derivative gravity tends to become a UV complete gravity theory.…”

Section: Jhep06(2020)152mentioning

confidence: 99%

Non-Gaussianities and tensor-to-scalar ratio in non-local R2-like inflation

Koshelev

Kumar

Mazumdar

et al. 2020

J. High Energ. Phys.

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In this paper we will study R 2-like inflation in a non-local modification of gravity which contains quadratic in Ricci scalar and Weyl tensor terms with analytic infinite derivative form-factors in the action. It is known that the inflationary solution of the local R + R 2 gravity remains a particular exact solution in this model. It was shown earlier that the power spectrum of scalar perturbations generated during inflation in the non-local setup remains the same as in the local R + R 2 inflation, whereas the power spectrum of tensor perturbations gets modified due to the non-local Weyl tensor squared term. In the present paper we go beyond 2-point correlators and compute the non-Gaussian parameter f NL related to 3-point correlations generated during inflation, which we found to be different from those in the original local inflationary model and scenarios alike based on a local gravity. We evaluate non-local corrections to the scalar bi-spectrum which give non-zero contributions to squeezed, equilateral and orthogonal configurations. We show that f NL ∼ O(1) with an arbitrary sign is achievable in this model based on the choice of form-factors and the scale of non-locality. We present the predictions for the tensor-toscalar ratio, r, and the tensor tilt, n t. In contrast to standard inflation in a local gravity, here the possibility n t > 0 is not excluded. Thus, future CMB data can probe non-local behaviour of gravity at high space-time curvatures.

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Section: Jhep06(2020)152mentioning

confidence: 99%

Non-Gaussianities and tensor-to-scalar ratio in non-local R2-like inflation

Koshelev

Kumar

Mazumdar

et al. 2020

J. High Energ. Phys.

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“…This choice of β also implies: (a) Unitality β th (0) = 0, (b) Reality β th (q) = β th (−q) ∈ R, and (c) Commutativity and Associativity assured by the first equality in (48). α th is bounded analytic everywhere in q-space, and its mathematical simplicity is also appealing.…”

Section: The Integral Kernel Twistmentioning

confidence: 99%

Commutatively deformed general relativity: foundations, cosmology, and experimental tests

Vegvar

2021

Eur. Phys. J. C

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An integral kernel representation for the commutative $$\star $$ ⋆ -product on curved classical spacetime is introduced. Its convergence conditions and relationship to a Drin’feld differential twist are established. A $$\star $$ ⋆ -Einstein field equation can be obtained, provided the matter-based twist’s vector generators are fixed to self-consistent values during the variation in order to maintain $$\star $$ ⋆ -associativity. Variations not of this type are non-viable as classical field theories. $$\star $$ ⋆ -Gauge theory on such a spacetime can be developed using $$\star $$ ⋆ -Ehresmann connections. While the theory preserves Lorentz invariance and background independence, the standard ADM $$3+1$$ 3 + 1 decomposition of 4-diffs in general relativity breaks down, leading to different $$\star $$ ⋆ -constraints. No photon or graviton ghosts are found on $$\star $$ ⋆ -Minkowski spacetime. $$\star $$ ⋆ -Friedmann equations are derived and solved for $$\star $$ ⋆ -FLRW cosmologies. Big Bang Nucleosynthesis restricts expressions for the twist generators. Allowed generators can be constructed which account for dark matter as arising from a twist producing non-standard model matter field. The theory also provides a robust qualitative explanation for the matter-antimatter asymmetry of the observable Universe. Particle exchange quantum statistics encounters thresholded modifications due to violations of the cluster decomposition principle on the nonlocality length scale $$\sim 10^{3-5} \,L_P$$ ∼ 10 3 - 5 L P . Precision Hughes–Drever measurements of spacetime anisotropy appear as the most promising experimental route to test deformed general relativity.

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“…This proposal for an ultraviolet completion of Einstein-Hilbert (EH) gravity was subsequently abandoned, since the specific models studied in [1][2][3][4] contain ineradicable ghosts. However, nonlocal models have been revisited in recent years [5][6][7][8][9][10][11], when it became clear that, under certain conditions that restrict the type of nonlocality, it is possible to avoid ghosts. In facts, it has been shown that the complex scattering amplitudes in nonlocal field theories satisfy the Cutkosky rules [12][13][14][15], so that the unitarity is preserved at any pertutbative order in the loop expansion.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, in order to achieve a renormalizable quantum theory of gravitational interactions, one is forced to introduce a new nonlocal or higher derivative action principle. In this paper we will focus on nonlocal quantum gravity [5][6][7][8][9][10][11], but most of the results reported here are still valid for other higher-derivative theories [16][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Unattainability of the trans-Planckian regime in nonlocal quantum gravity

Briscese

Modesto

2020

J. High Energ. Phys.

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Based on the ultraviolet asymptotic freedom of nonlocal quantum gravity, we show that the trans-Planckian energy regime is unattainable in laboratory experiments. As physical implications, it turns out that the violation of causality, typical of nonlocal field theories, can never be detected in particle accelerators, while the asymptotic freedom of the theory provides an elegant solution to the so called trans-Planckian cosmological problem.

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Generalized ghost-free propagators in nonlocal field theories

Cited by 47 publications

References 184 publications

Non-Gaussianities and tensor-to-scalar ratio in non-local R2-like inflation

Non-Gaussianities and tensor-to-scalar ratio in non-local R2-like inflation

Commutatively deformed general relativity: foundations, cosmology, and experimental tests

Unattainability of the trans-Planckian regime in nonlocal quantum gravity

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