Absence of Relativistic Stars in f(T) Gravity

Deliduman, Cemsinan; Yapişkan, Barış

doi:10.48550/arxiv.1103.2225

Cited by 33 publications

(46 citation statements)

References 18 publications

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“…f ,T T = 0 puts a strict restriction on the choice of f (T ) function to a linear one. As a result, only if f (T ) is a linear function of the torsion scalar T , one can leads to the existence of neutron star solution [92]. In a recent paper, [91,92] suggested that, instead of choosing f ,T T = 0, if one consider T ′ = 0 or T = T 0 , the solution yields a constant energy density and pressure, obeying the dark energy equation of state or the pressure which blows up at r → 0.…”

Section: Resultsmentioning

confidence: 99%

Einstein's cluster mimicking compact star in the teleparallel equivalent of general relativity

Singh,

Rahaman,

Banerjee

2019

Preprint

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We present a physically plausible solution representing Einstein's cluster mimicking the behaviors of compact star in the context of teleparallel equivalent of general relativity. The Teleparallel gravity (TEGR) is an alternative formulation of gravity which uses tetrads as the dynamical variables. We focus on two particularly interesting scenarios. First, we develop the Einstein clusters in TEGR field equations using effective energy-momentum tensor for diagonal as well as off-diagonal tetrad. We then study the clusters in modified f (T )−gravity for anisotropic fluid distribution. Based on these two theories, we further study the solution without net electric charge and then for charged solution. For charge parameter k → 0, the charged solution reduces to neutral one. Our calculations show that when charge increases, the stiffness of the EoS also increases. This is due to increase in adiabatic index and sound speed approaching speed of light. When the charge increase beyond a certain limit (0 ≤ k ≤ 1.3 × 10 −5 and 0 ≤ k ≤ 1 × 10 −6 ), the compactness parameter crosses the Buchdahl limit i.e. 2M/R > 8/9 and the solution start violating the causality condition. We test the Tolman-Oppenheimer-Volkoff (TOV) limit for such compact objects. We analyze the static stability criterion of the Einstein clusters for both charged and uncharged case, and the stability of such compact objects is enhanced by the presence some net electric charge. In addition, we present and discuss the energy conditions, causality condition and the adiabatic index close to the stability limit. After analyzing these problems, we conclude that the Einstein clusters do exists only if f (T ) is a linear function of the torsion scalar T , that is in the case of Teleparallel Equivalent of General Relativity. Finally, we compare our solution for pure general relativity. As a result, we concluded that the Einstein cluster solution do exist in pure GR, however, physically unfit to mimic compact stars. We have also extend our findings by assuming the diagonal or off-diagonal tetrad and specific case of f (T ). In such models, Einstein's cluster solutions do exist however can't mimic the properties of a compact star.

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Section: Resultsmentioning

confidence: 99%

Einstein's cluster mimicking compact star in the teleparallel equivalent of general relativity

Singh,

Rahaman,

Banerjee

2019

Preprint

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“…The equations of motion of the non-diagonal case are quite different from the previous ones of the diagonal case. This is the proof of the dependence on the frame in f (T ) theory [26]. In such a situation, the physics that results from this set of equations must present new data that may be important in understanding the subjects that still require attention in Cosmology and Astrophysics.…”

Section: A Set Of Non-diagonal Tetradmentioning

confidence: 85%

“…An imposition of the form (26) has been obtained for a set of diagonal tetrads in the case of a spherically symmetric and static metric [19,20]. In the next section, we will see the case where it will be taken a set of non-diagonal tetrads for describing the metric of LTB (18).…”

Section: The Geometry Of An Inhomogeneous Universementioning

confidence: 99%

Inhomogeneous universe in f(T) theory

et al. 2014

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We obtain the equations of motions of the f (T ) theory considering the Lemaître-TolmanBondi's metric for a set of diagonal and non-diagonal tetrads. In the case of diagonal tetrads the equations of motion of the f (T ) theory impose a constant torsion or the same equations of the General Relativity, while in the case of non-diagonal set the equations are quite different from that obtained in GR. We show a simple example of an universe dominated by the matter for the two cases. The comparison of the mass in the non-diagonal case shows a sort of increased with respect to the diagonal one. We also perform two examples for the nondiagonal case. The first concerns a black hole solution of type Sshwarzschild which presents a temperature higher than that of Schwarzschild, and a black hole in a dust-dominated universe.

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“…Deliduman and Yapiskan [24] have observed the constraint on the neutron solution in f (T ) theory of gravity and concluded that the solution is possible only for a linear function of torsion. Cai et al [25] have discussed the matter bounce cosmology with scalar and tensor modes of cosmological perturbations.…”

Section: Introductionmentioning

confidence: 99%

A New Proposal for Galactic Dark Matter: Effect of f(T) Gravity

Rahaman

Biswas²,

Fatima³

et al. 2013

Int J Theor Phys

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It is still a challenging problem to the theoretical physicists to know the exact nature of the galactic dark matter which causes the galactic rotational velocity to be more or less a constant. We have proposed the dark matter as an effect of f(T) gravity. Assuming the flat rotation curves as input we have shown that f(T) gravity can explain galactic dynamics. Here, we do not have to introduce dark matter. Spacetime metric inspired by f(T) gravity describes the region up to which the tangential velocity of the test particle is constant. This inherent property appears to be enough to produce stable circular orbits as well as attractive gravity.

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Absence of Relativistic Stars in f(T) Gravity

Cited by 33 publications

References 18 publications

Einstein's cluster mimicking compact star in the teleparallel equivalent of general relativity

Einstein's cluster mimicking compact star in the teleparallel equivalent of general relativity

Inhomogeneous universe in f(T) theory

A New Proposal for Galactic Dark Matter: Effect of f(T) Gravity

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