Linear and second-order geometry perturbations on spacetimes with torsion

Izaurieta, Fernando; Rodríguez, Evelyn; Valdivia, Omar

doi:10.1140/epjc/s10052-019-6852-y

Cited by 11 publications

(13 citation statements)

References 26 publications

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“…The differential operators we define appeared originally in Refs. [51,69,76]; here we briefly review them for the benefit of the reader who may be unfamiliar with them. We also show that these operators form a superalgebra and identify its associated super-Jacobi identity, which, beyond the merely aesthetic, eases the study of the eikonal limit of GWs on an RC geometry.…”

Section: A a Superalgebra Of Differential Operatorsmentioning

confidence: 99%

“…In Ref. [76], it was shown that they can be described up to second order through the perturbations in the vierbein and the spin connection given by e a →ē a = e a + 1 2 H a ,…”

Section: Perturbations On a Riemann-cartan Geometrymentioning

confidence: 99%

“…Without loss of generality, its orthonormal-frame components can be taken as symmetric, H ba = H ab for any Lorentz-invariant theory [76]. The perturbation on the spin connection comes in two pieces, U ab (H, ∂H) and V ab .…”

Section: Perturbations On a Riemann-cartan Geometrymentioning

confidence: 99%

“…Section VI focuses on the leading high-frequency term to prove that torsion restores the canonical dispersion relation, including speed, for the metric mode of GWs. The eikonal approximation is used to show that the new torsional mode (variously called "torsionon" [76], "roton" [77], or "gravity W and Z bosons" [78]) propagates interacting with the polarization of the standard metric mode, generalizing the results of Ref. [69].…”

Section: Introductionmentioning

confidence: 99%

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Luminal propagation of gravitational waves in scalar-tensor theories: The case for torsion

et al. 2019

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Scalar-tensor gravity theories with a nonminimal Gauss-Bonnet coupling typically lead to an anomalous propagation speed for gravitational waves, and have therefore been tightly constrained by multimessenger observations such as GW170817/GRB170817A. In this paper we show that this is not a general feature of scalar-tensor theories, but rather a consequence of assuming that spacetime torsion vanishes identically. At least for the case of a nonminimal Gauss-Bonnet coupling, removing the torsionless condition restores the canonical dispersion relation and therefore the correct propagation speed for gravitational waves. To achieve this result we develop a new approach, based on the first-order formulation of gravity, to deal with perturbations on these Riemann-Cartan geometries.topological invariants, e.g., the Pontryagin or Gauss-Bonnet (GB) terms, motivated by effective field theories, string theory, and particle physics [15]. From a phenomenological viewpoint, the scalar-Pontryagin modification to GR-also known as Chern-Simons modified gravity-is an interesting extension that might explain the flat galaxy rotation curves dispensing with dark matter [16], while leaving the propagation speed of GWs unaffected [17]. This interaction generates nontrivial effects when rotation is included [18][19][20][21][22][23], providing a smoking gun in future GW detectors [24][25][26][27]. The couplings between scalar fields and the GB term, on the other hand, have been studied in different setups and several solutions that exhibit spontaneous scalarization have been reported [28][29][30][31][32][33][34][35][36][37][38][39][40][41]. Their stability, however, depends on the choice of the coupling between the scalar field and the GB term [42][43][44]. In spite of this, the theory is experimentally disadvantaged from an astrophysical viewpoint, since it develops an anomalous propagation speed for GWs [45].Scalar-tensor theories have been formulated in geometries that depart from the pseudo-Riemannian framework several times in the past. In particular, the gravitational role of Riemann-Cartan (RC) geometries, characterized by curvature and torsion, was first discussed by Cartan and Einstein themselves [46], and later on in the framework of gauge theories of gravitation [47][48][49][50]. Within its simplest formulation-the Einstein-Cartan-Sciama-Kibble (ECSK) theory-torsion is a nonpropagating field sourced only by the spin density of matter. The nonminimal coupling of scalar fields to geometry dramati-arXiv:1910.00148v3 [gr-qc]

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Section: A a Superalgebra Of Differential Operatorsmentioning

confidence: 99%

“…In Ref. [76], it was shown that they can be described up to second order through the perturbations in the vierbein and the spin connection given by e a →ē a = e a + 1 2 H a ,…”

Section: Perturbations On a Riemann-cartan Geometrymentioning

confidence: 99%

Section: Perturbations On a Riemann-cartan Geometrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Luminal propagation of gravitational waves in scalar-tensor theories: The case for torsion

et al. 2019

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“…Although being difficult to obtain experimental evidence about the real effects of space-time torsion, once that such effects require a high energy density at cosmological events, there are predictive studies of how torsion signatures could manifest via inflation [23,24] and gravitational waves [25,26]. In the works [27,28] there are interesting studies and suggestions for experimental tests of non-zero torsion for gravity, concerning the Moon and Mercury motion.…”

Section: Introductionmentioning

confidence: 99%

Cosmological inflation driven by a scalar torsion function

2021

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A viable model for inflation driven by a torsion function in a Friedmann background is presented. The scalar spectral index in the interval $$0.92\lesssim n_{s}\lesssim 0.97$$ 0.92 ≲ n s ≲ 0.97 is obtained in order to satisfy the initial conditions for inflation. The post inflationary phase is also studied, and the analytical solutions obtained for scale factor and energy density generalizes that ones for a matter dominated universe, indicating just a small deviation from the standard model evolution. The same kind of torsion function used also describes satisfactorily the recent acceleration of the universe, which could indicate a possible unification of different phases, apart form specific constants

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