On the junction conditions in $f(R)$ -gravity with torsion

Vignolo, Stefano; Cianci, Roberto; Carloni, Sante

doi:10.1088/1361-6382/aab6fe

Cited by 24 publications

(20 citation statements)

References 46 publications

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“…The Israel procedure was initially developed for space-times in the absence of torsion. More recently, a number of works have been published in which the junction conditions are generalized to space-times with torsion in different contexts [42,43]. Here we will summarize the results and extend them in light of the structure equations we have just obtained.…”

Section: Junction Conditionsmentioning

confidence: 64%

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Static compact objects in Einstein-Cartan theory

Luz

Carloni

2019

Phys. Rev. D

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We generalize the Tolman-Oppenheimer-Volkoff equations for space-times endowed with a Weyssenhoff like torsion field in the Einstein-Cartan theory. The new set of structure equations clearly show how the presence of torsion affects the geometry of the space-time. We obtain new exact solutions for compact objects with non-null intrinsic spin surrounded by vacuum, explore their properties and discuss how these solutions should be smoothly matched to an exterior space-time.We study how the intrinsic spin of matter changes the Buchdahl limit for the maximum compactness of stars. Moreover, under rather generic conditions, we prove that in the context of a Weyssenhoff like torsion, no static, spherically symmetric compact objects supported only by the intrinsic spin can exist. We also provide some algorithms to generate new solutions. * paulo.luz@ist.utl.pt † sante.carloni@gmail.com 1 We should remark that here, and in the following, the word "spin" will be used exclusively to represent the quantum spin of the particles that source the gravitational field equations. In no case the word spin will be associated to any form of rotation of the compact objects we will analyze.

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Section: Junction Conditionsmentioning

confidence: 64%

“…Now, following Ref. [43], for the total space-time to be a valid solution of the the field equations and to guarantee that at N there is no surface layer, the following conditions must be met:…”

Section: Junction Conditionsmentioning

confidence: 99%

Static compact objects in Einstein-Cartan theory

Luz

Carloni

2019

Phys. Rev. D

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“…According to this modification, the expression for the stress-energy tensor of the shell is formally the same one as in general relativity but the tensor representing the jump of the transverse derivatives of the metric is replaced with a non-symmetric one splitting into a Riemann part and a Cartan part. Recently, using the Bressange's approach [7], the junction conditions of two generic spacetimes through a non-lightlike hypersurface in the context of f(R) gravity with torsion has been derived via the definition of a suitable effective extrinsic curvature tensor which splits into a Riemann part and a Cartan one. There is another approach to generalize the junction conditions for a singular hypersurface within the EC gravity applied to the Braneworld scenarios [8].…”

Section: Introductionmentioning

confidence: 99%

On the stress–energy tensor of a null shell in Einstein–Cartan gravity

Khakshournia¹,

Mansouri²

2019

Class. Quantum Grav.

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The stress-energy tensor of a matter shell whose history coincides with a null hypersurface in the Einstein-Cartan gravity is revisited. It is demonstrated that with a proper choice for the torsion discontinuity taken to be orthogonal to the null hypersurface and consistent with the antisymmetric property of torsion tensor, the modified expression for the asymmetric stress-energy tensor is automatically tangent to the hypersurface. The main differences with respect to a previous work are addressed.

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“…Later, scientists discovered that the terms which are related to the quantum higher order corrections are responsible for the accelerating expansion rate of our universe at large structures. This phenomenon has been investigated at the fourth order of f (R) [6][7][8][9][10][11][12][13] (for more references on modified gravity theories as well as dark energy problem, see, e.g., [14,15]). The mechanism which determines the difference between f (R) gravitational theories and the Einstein general relativity (GR), that is ensured to be detected at the scales of astrophysics and strong gravitational field, is to derive black holes that are different from those of GR (vacuum or electro-vacuum) [16][17][18][19][20][21].…”

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confidence: 99%

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confidence: 99%

Charged spherically symmetric Taub–NUT black hole solutions in $f(R)$ gravity

Nashed

Bamba

2020

Progress of Theoretical and Experimental Physics

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f (R) theory is a modification of Einstein general relativity which has many interesting results in cosmology and astrophysics. To derive solutions for black holes solution in this theory is difficult due to the fact that it is fourth order differential equations. In this study, we use the quadratic form of f (R) = R + βR 2 − 2Λ, where β is a dimensional parameter and Λ is the cosmological constant, to find the solutions of new 4-dimension spherically symmetric non-charged and charged NUT and Taub-NUT black holes. An interesting property for these black holes is the fact that NUT spacetime has a non-vanishing value of the magnetic field, while Taub-NUT one does magnetic and electric fields. We calculate the energy conditions of the charged black holes and show that all of them are satisfied for the Taub-NUT spacetime. Finally, we study some thermodynamic quantities such as entropy, temperature, specific heat and Gibbs free energy. The calculations of heat capacity and free energy show that the charged NUT and Taub NUT black holes have local stability.Recently, observations confirm that our universe suffers from acceleration. Since that, the correspondence between the accelerated epoch and the inflationary mechanism help scientists to assume that dark energy may have a geometric origin [3][4][5]. Later, scientists discovered that the terms which are related to the quantum higher order corrections are responsible for the accelerating expansion rate of our universe at large structures. This phenomenon has been investigated at the fourth order of f (R) [6][7][8][9][10][11][12][13] (for more references on modified gravity theories as well as dark energy problem, see, e.g., [14,15]).The mechanism which determines the difference between f (R) gravitational theories and the Einstein general relativity (GR), that is ensured to be detected at the scales of astrophysics and strong gravitational field, is to derive black holes that are different from those of GR (vacuum or electro-vacuum) [16][17][18][19][20][21]. There are many applications carried out on f (R), among them are: The one-loop effective action of f (R) theories on the de-Sitter background that has been explained in [22]. One of the most interesting phenomena which can occur in charged black hole solutions is the anti-evaporation process which explains the primordial black hole. In order that the anti-evaporation may occur in the Einstein theory, one needs to involve the quantum correction terms from the matter field. Anti-evaporation could occur at the classical level on modified gravity theories like f (R) gravity [23,24]. A subject to acquire solutions for static spherically symmetric black holes in f (R) gravity has been addressed in [25]. In f (R) gravity, solutions for spherically symmetric black holes have been obtained by assuming that the scalar curvature is constant [26][27][28]. Also, spherically symmetric non-charged and charged black hole solutions have been discussed with no constraints on the scalar curvature and the Ricci tensor in [29][30][31]....

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On the junction conditions in $f(R)$ -gravity with torsion

Cited by 24 publications

References 46 publications

Static compact objects in Einstein-Cartan theory

Static compact objects in Einstein-Cartan theory

On the stress–energy tensor of a null shell in Einstein–Cartan gravity

Charged spherically symmetric Taub–NUT black hole solutions in $f(R)$ gravity

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