Theoretical cosmology

Coley, A. A.; Ellis, George

doi:10.1088/1361-6382/ab49b6

Cited by 35 publications

(29 citation statements)

References 451 publications

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“…Nevertheless, we have shown that in our model the homogeneous solution approximate quite well the inhomogeneous one, thus the effect of small-scale inhomogeneities is not an 'order of magnitude effect', but it introduces a small correction. This conclusion is consistent with results obtained using different approaches [16,18] (assuming that local effects are negligible) and the current state-of-the-art of this topic (see the article [23] and references therein).…”

Section: Discussionsupporting

confidence: 91%

“…This type of solutions have interesting properties that allow for novel studies of the effect of small-scale inhomogeneities in an alternative setting. Our research is restricted to a simple toy-model and, as such, it is only indirectly relevant for cosmology (for other studies based on exact solutions see also [16][17][18][19][20][21][22]; for the current review of cosmological backreaction see [23]).…”

Section: Introductionmentioning

confidence: 99%

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Einstein clusters as models of inhomogeneous spacetimes

Szybka

Rutkowski

2020

Eur. Phys. J. C

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We study the effect of small-scale inhomogeneities for Einstein clusters. We construct a spherically symmetric static spacetime with small-scale radial inhomogeneities and propose the Gedankenexperiment. An hypothetical observer at the center constructs, using limited observational knowledge, a simplified homogeneous model of the configuration. An idealization introduces side effects. The inhomogeneous spacetime and the effective homogeneous spacetime are given by simple solutions to Einstein equations. They provide a basic toy-model for studies of the effect of small-scale inhomogeneities in general relativity. We show that within our highly inhomogeneous model the effect of small-scale inhomogeneities remains small for a central observer. The homogeneous model fits very well to all hypothetical observations as long as their precision is not high enough to reveal a tension.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Einstein clusters as models of inhomogeneous spacetimes

Szybka

Rutkowski

2020

Eur. Phys. J. C

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“…This modified theory has come to be known as the f (R) theory of gravity. Stellar modeling in f (R) gravity has received interest in the recent past which produced models which are compatible with observational data, see [8] and references therein. However, some recent works on the f (R; T ) theory, Rastall theory and Starobinsky f (R; T )-function can be seen in the following Refs.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic stars via embedding approach in Brans–Dicke gravity

et al. 2021

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In the present article, the solution of the Einstein–Maxwell field equations in the presence of a massive scalar field under the Brans-Dicke (BD) gravity is obtained via embedding approach, which describes a charged anisotropic strange star model. The interior spacetime is described by a spherically symmetric static metric of embedding class I. This reduces the problem to a single-generating function of the metric potential which is chosen by appealing to physics based on regularity at each interior point of the stellar interior. The resulting model is subjected to rigorous physical checks based on stability, causality and regularity for particular object PSR J1903+327. We also show that our solutions describe compact objects such as PSR J1903+327; Cen X-3; EXO 1785-248 and LMC X-4 to an excellent approximation. Novel results of our investigation reveal that the scalar field leads to higher surface charge densities which in turn affects the compactness and upper and lower values imposed by the modified Buchdahl limit for charged stars. Our results also show that the electric field and scalar field which originate from entirely different sources couple to alter physical characteristics such as mass-radius relation and surface redshift of compact objects. This superposition of the electric and scalar fields is enhanced by an increase in the BD coupling constant, $$\omega _{BD}$$ ω BD .

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“…Modern cosmology [1] encourages various models of dark matter to explain the observed constancy of the azimuthal velocity of stars at ultra-large distances (up to 200 kpc) from the galactic axis, where gravity is very weak and space is Euclidean. Proponents of dark matter substantiated its existence through the Keplerian motion under the inverse square force, which is well-proven in the Solar System.…”

Section: Introductionmentioning

confidence: 99%

Self-rotation of emitting galaxies without dark matter

Bulyzhenkov

2021

Eur. Phys. J. C

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Temporal derivatives of the attracting mass in Newton’s law of distant interactions can balance the centripetal and centrifugal accelerations for the rotating periphery of a spiral galaxy. Thermal losses of the mass-energy integral inside the circle of rotation are the cause of the mega-vortex organization of the emitting galaxy. To reject dark matter in cosmic distributions, a conceptual modification of the Euler/Navier–Stokes hydrodynamics is required using adaptive tensor responses with metric waves but not gravimagnetic corrections from General Relativity.

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Theoretical cosmology

Abstract: We review current theoretical cosmology, including fundamental and mathematical cosmology and physical cosmology (as well as cosmology in the quantum realm), with an emphasis on open questions.

Cited by 35 publications

References 451 publications

Einstein clusters as models of inhomogeneous spacetimes

Einstein clusters as models of inhomogeneous spacetimes

Anisotropic stars via embedding approach in Brans–Dicke gravity

Self-rotation of emitting galaxies without dark matter

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