Nonminimal couplings, gravitational waves, and torsion in Horndeski’s theory

Barrientos, José; Cordonier-Tello, Fabrizio; Izaurieta, Fernando; Medina, Perla; Narbona, Daniela; Rodríguez, Evelyn; Valdivia, Omar

doi:10.1103/physrevd.96.084023

Cited by 30 publications

(40 citation statements)

References 55 publications

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“…(19)- (25) and Ref. [51]. In this sense, the torsionless condition amounts to an unproven hypothesis.…”

Section: Conclusion and Future Possibilitiesmentioning

confidence: 97%

“…The Lagrangian (1) allows for propagating torsion in vacuum and can be regarded as both a particular case of Horndeski's theory [80] and as a generalization of dynamical Chern-Simons modified gravity [15,81], both of which set the torsion equal to zero at the outset (but see Ref. [51] for the torsional version of Horndeski's theory). The theory defined by Eq.…”

Section: Scalar-tensor Model With Gauss-bonnet Couplingmentioning

confidence: 99%

“…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%

“…A first generalization was put forward in Ref. [51], but, while correct, it proved to be far from the best choice: the final result was a cumbersome inhomogeneous GW equation with many torsional couplings.…”

Section: A Lie Draggings and Lorentz Transformationsmentioning

confidence: 99%

“…Definition 8 (Generalized Beltrami-Laplace wave operator). We define the generalized Beltrami-Laplace wave operator B : Ω p (M ) → Ω p (M ) by[51] …”

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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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“…(19)- (25) and Ref. [51]. In this sense, the torsionless condition amounts to an unproven hypothesis.…”

Section: Conclusion and Future Possibilitiesmentioning

confidence: 97%

Section: Scalar-tensor Model With Gauss-bonnet Couplingmentioning

confidence: 99%

Section: A a Superalgebra Of Differential Operatorsmentioning

confidence: 99%

Section: A Lie Draggings and Lorentz Transformationsmentioning

confidence: 99%

“…Definition 8 (Generalized Beltrami-Laplace wave operator). We define the generalized Beltrami-Laplace wave operator B : Ω p (M ) → Ω p (M ) by[51] …”

mentioning

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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A black hole solution in conformal supergravity

Alvarez

Corral

Zanelli

2023

J. High Energ. Phys.

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We present a three-parameter family of analytic black-hole solutions in the bosonic sector of a four-dimensional supersymmetric model with matter fields in the adjoint representation. The solutions are endowed with a curvature and torsional singularities which are both surrounded by an event horizon. They are asymptotically Lorentz flat, representing the torsional generalization of the Riegert black hole in conformal gravity. We compute the partition function to first order in the saddle-point approximation which turns out to be finite without any reference to boundary counterterms. We find a non-maximmally symmetric thermalized ground state, whose existence is relevant when studying Hawking-Page phase transitions. Finally, we discuss future directions regarding its extended phase space.

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Holographic renormalization of Horndeski gravity

Cáceres,

Corral,

Díaz

et al. 2024

J. High Energ. Phys.

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We study the renormalization of a particular sector of Horndeski theory. In particular, we focus on the nonminimal coupling of a scalar field to the Gauss-Bonnet term and its kinetic coupling to the Einstein tensor. Adopting a power expansion on the scalar function that couples the Gauss-Bonnet term, we find specific conditions on their coefficients such that the action and charges are finite. To accomplish the latter, we add a finite set of intrinsic boundary terms. The contribution of the nonminimal coupling generates an effective scalar mass, allowing us to recover a modified Breitenlohner-Freedman bound. Furthermore, we compute the holographic 1-point functions and Ward identities associated with the scalar field and the metric. We constrain the parameter space of the theory by taking into account the preservation of scaling symmetry at the boundary.

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Nonminimal couplings, gravitational waves, and torsion in Horndeski’s theory

Cited by 30 publications

References 55 publications

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

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

A black hole solution in conformal supergravity

Holographic renormalization of Horndeski gravity

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