Black branes and black strings in the astrophysical and cosmological context

Akarsu, Özgür; Chopovsky, Alexey; Zhuk, Alexander

doi:10.1016/j.physletb.2018.01.022

Cited by 7 publications

(8 citation statements)

References 36 publications

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“…The gravitating mass perturbs also the background metrics (1). Since the gravitating source is spherically symmetric and pressure in each factor space is isotropic, the perturbed metrics preserves its block-diagonal form (for mathematical justification of this claim, see [12]):…”

Section: Background and Perturbed Modelsmentioning

confidence: 99%

“…First, we consider the diagonal components of the Einstein equation (12). To get the expressions for the components of the Ricci tensor, we can use the results of Appendix A in [8].…”

Section: Background and Perturbed Modelsmentioning

confidence: 99%

“…Obviously, such multidimensional theories should not contradict the experimental data, in particular, the well-known gravitational tests in the Solar system: deflection of light, time delay of radar echoes and perihelion precession of Mercury. We investigated this problem in a number of our previous papers [5][6][7][8][9][10][11][12] and one of the main conclusions of these papers is that in the case of Ricci-flat internal spaces, the model with pressureless gravitating mass contradicts gravitational tests [5]. The negative result follows as a consequence of massless fluctuations of the internal space that generate the fifth force [13].…”

Section: Introductionmentioning

confidence: 99%

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Weak-Field Limit of a Kaluza-Klein Model with a Nonlinear Perfect Fluid

Yalçınkaya

Zhuk

2019

Gravit. Cosmol.

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The main purpose of our paper is to construct a viable Kaluza-Klein model satisfying the observable constraints. To this end, we investigate the six-dimensional model with spherical compactification of the internal space. Background matter is considered in the form of a perfect fluid with non-linear equations of state both in the external/our and internal spaces and the model is set to include an additional bare cosmological constant Λ 6 . In the weak-field approximation, the background is perturbed by pressureless gravitating mass that is a static point-like particle. The non-linearity of the equations of state of a perfect fluid makes it possible to solve simultaneously a number of problems. The demand that the parameterized post-Newtonian parameter γ be equal to 1 in this configuration, first, ensures compatibility with gravitational tests in the Solar system (deflection of light and time delay of radar echoes) at the same level of accuracy as General Relativity. Second, it translates into the absence of internal space variations so that the gravitational potential coincides exactly with the Newtonian one, securing the absence of the fifth force. Third, the gravitating mass remains pressurless in the external space as in the standard approach to non-relativistic astrophysical objects and meanwhile, acquires effective tension in the internal space. *

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Section: Background and Perturbed Modelsmentioning

confidence: 99%

“…First, we consider the diagonal components of the Einstein equation (12). To get the expressions for the components of the Ricci tensor, we can use the results of Appendix A in [8].…”

Section: Background and Perturbed Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Weak-Field Limit of a Kaluza-Klein Model with a Nonlinear Perfect Fluid

Yalçınkaya

Zhuk

2019

Gravit. Cosmol.

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“…The only nonzero components of the EMT are, then,T 0 0 ≈ρc 2 andT i k ≈ −δ i k Ωρc 2 for i, k = 4, 5. Such type of perturbation preserves the blockdiagonal form of the perturbed metric [31,35]:…”

Section: Basic Equationsmentioning

confidence: 99%

“…To make the background curved, one needs to introduce a background perfect fluid. The linear multidimensional models with spherical compactification of the internal space were considered in [31][32][33][34][35]. It was shown that the background matter responsible for the internal space curvature has the vacuum-like EoS parameterω 0 = −1 in the external space and some positive EoS parameterω 1 > 0 in the internal space.…”

Section: Introductionmentioning

confidence: 99%

Effects of nonlinearity of f(R) gravity and perfect fluid in Kaluza–Klein models with spherical compactification

2020

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We study the effects associated with nonlinearity of f(R) gravity and of the background perfect fluid manifested in the Kaluza–Klein model with spherical compactification. The background space-time is perturbed by a massive gravitating source which is pressureless in the external space but has an arbitrary equation of state (EoS) parameter in the internal space. As characteristics of a nonlinear perfect fluid, the squared speeds of sound are not equal to the background EoS parameters in the external and internal spaces. In this setting, we find exact solutions to the linearized Einstein equations for the perturbed metric coefficients. For nonlinear models with $$f^{\prime \prime }(R_0)\ne 0$$f″(R0)≠0, we show that these coefficients acquire correction terms in the form of two summed Yukawa potentials and that in the degenerated case, the solutions are reduced to a single Yukawa potential with some “corrupted” prefactor (in front of the exponential function), which, in addition to the standard 1/r term, contains a contribution independent of the three-dimensional distance r. In the linear $$f''(R)=0$$f′′(R)=0 model, we generalize the previous studies to the case of an arbitrary nonlinear perfect fluid. We also investigate the particular case of the nonlinear background perfect fluid with zero speed of sound in the external space and demonstrate that a non-trivial solution exists only in the case of $$f''(R_0)=0$$f′′(R0)=0.

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ACDM cosmology with a quiescent anisotropy in a higher dimensional steady state universe

Akarsu

Dereli

Katırcı

2022

J. Phys.: Conf. Ser.

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In this work, which follows a series of studies on the higher-dimensional steady state universe idea and prepared for Professor Tekin Dereli’s Festschrift, we show the infuence of the dynamical internal (unobservable) space on the evolution of the possible anisotropy of the external (observable) space. We obtain mathematically exactly the same Friedmann equation of the standard ΛCDM model for the external space, but with some remarkable physical diferences. In particular, the higher-dimensional negative cosmological constant plays the role of the four-dimensional positive cosmological constant and the expansion anisotropy, viz., the shear scalar, of the external space mimics a negative cosmological constant; it would mimic a stif fuid when allowed on top of the standard ΛCDM model. This latter feature gives us the opportunity to manipulate the CMB quadrupole temperature fuctuation, suggesting a possible answer to the fact that its observed value is lower than that predicted by the standard ΛCDM model.

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Black branes and black strings in the astrophysical and cosmological context

Cited by 7 publications

References 36 publications

Weak-Field Limit of a Kaluza-Klein Model with a Nonlinear Perfect Fluid

Weak-Field Limit of a Kaluza-Klein Model with a Nonlinear Perfect Fluid

Effects of nonlinearity of f(R) gravity and perfect fluid in Kaluza–Klein models with spherical compactification

ACDM cosmology with a quiescent anisotropy in a higher dimensional steady state universe

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