Ghost instability in the teleparallel gravity model with parity violations

Li, Mingzhe; Li, Zhihao; Rao, Haomin

doi:10.48550/arxiv.2201.02357

Cited by 4 publications

(4 citation statements)

References 25 publications

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“…Finally, a local Lorentz covariant version of [349] was considered in [351] and non-flat universes were also taken into account. It was recently reported that some TG parity-violating models suffer from ghost instabilities but the so-called modified TG Nieh-Yan is free of them [352].…”

Section: Other Approachesmentioning

confidence: 99%

Teleparallel gravity: from theory to cosmology

et al. 2023

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Teleparallel gravity has significantly increased in popularity in recent decades, bringing attention to Einstein’s other theory of gravity. In this Review, we give a comprehensive introduction to how teleparallel geometry is developed as a gauge theory of translations together with all the other properties of gauge field theory. We also related this form of geometry to the broader metric-affine approach to forming gravitational theories where we describe a systematic way of constructing consistent teleparallel theories that respect certain physical conditions such as local Lorentz invariance. We first use teleparallel gravity to formulate a teleparallel equivalent of general relativity which is dynamically equivalent to general relativity but which may have different behaviors for other scenarios, such as quantum gravity. After setting this foundation, we describe the plethora of modified teleparallel theories of gravity that have been proposed in the literature. We attempt to connect them together into general classes of covariant gravitational theories. Of particular interest, we highlight the recent proposal of a teleparallel analogue of Horndeski gravity which offers the possibility of reviving all of the regular Horndeski contributions. In the second part of the Review, we first survey works in teleparallel astrophysics literature where we focus on the open questions in this regime of physics. We then discuss the cosmological consequences for the various formulations of teleparallel gravity. We do this at background level by exploring works using various approaches ranging from dynamical systems to Noether symmetries, and more. Naturally, we then discuss perturbation theory, firstly by giving a concise approach in which this can be applied in teleparallel gravity theories and then apply it to a number of important theories in the literature. Finally, we examine works in observational and precision cosmology across the plethora of proposal theories. This is done using some of the latest observations and is used to tackle cosmological tensions which may be alleviated in teleparallel cosmology. We also introduce a number of recent works in the application of machine learning to gravity, we do this through deep learning and Gaussian processes, together with discussions about other approaches in the literature.

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Section: Other Approachesmentioning

confidence: 99%

Teleparallel gravity: from theory to cosmology

et al. 2023

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“…Alternatively, if we start from Teleparallel Equivalent of General Relativity (TEGR) [33][34][35][36], we will obtain a family of torsion-based modified gravity [37,38]. These torsional gravities provide new possible mechanisms for cosmological observations, such as inflation and accelerated expansion, and are highly considered and widely studied [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. It is worth noting that these modifications are efficient under confrontation with galaxy-scale observations too [56,57].…”

Section: Introductionmentioning

confidence: 99%

Gaussian processes and effective field theory of $f(T)$ gravity under the $H_0$ tension

Ren,

Yan,

Zhao

et al. 2022

Preprint

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We consider the effective field theory formulation of torsional gravity in a cosmological framework to alter the background evolution. Then we use the latest H0 measurement from the SH0ES Team as well as observational Hubble data from cosmic chronometer (CC) and radial baryon acoustic oscillations (BAO) and we reconstruct the f (T ) form in a model-independent way by applying Gaussian processes. Since the special square-root term does not affect the evolution at the background level, we finally result to a family of functions that can produce the background evolution required by the data. Finally, performing a fitting using polynomial functions we find an analytic expression that may describe the cosmological evolution in great agreement with observations.

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“…More recently, it was found in Ref. [21] that generalizations of NYTG by considering the couplings of φ to other parity-odd terms quadratic in the torsion tensor [22] are perplexed by the ghost problem again. It means in this scenario the NYTG model is the unique one that can avoid the ghost problem.…”

Section: Introductionmentioning

confidence: 99%

Possible consistent model of parity violations in the symmetric teleparallel gravity

Li,

Tong,

Zhao

2022

Preprint

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Many parity violating gravity models suffer from the ghost instability problem. In this paper we consider a symmetric teleparallel gravity model which extends the general relativity equivalent model by several parity violating interactions between the gravitational field and a scalar field. These interactions exclude higher derivatives and are quadratic in the non-metricity tensor. Through investigations on the linear cosmological perturbations, our results show that in general this model suffers from the difficulty caused by the existence of ghost mode in the vector perturbations. However, in cases where a special condition is imposed on the coefficients of these parity violating interactions, this model can be ghost free.

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Ghost instability in the teleparallel gravity model with parity violations

Cited by 4 publications

References 25 publications

Teleparallel gravity: from theory to cosmology

Teleparallel gravity: from theory to cosmology

Gaussian processes and effective field theory of $f(T)$ gravity under the $H_0$ tension

Possible consistent model of parity violations in the symmetric teleparallel gravity

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