scholarly journals Extended General Relativity for a Curved Universe

2020 ◽  
Author(s):  
Mohammed B. Al-Fadhli
Keyword(s):  
General Relativity ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
Positive Curvature ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Microwave Background ◽  
Cold Dark Matter Model ◽  
Order Of Magnitude ◽  
Dark Matter Model

The Planck Legacy recent release revealed the presence of an enhanced lensing amplitude in the cosmic microwave background, which confirms the early universe positive curvature with a confidence level exceeding 99%. Besides, the observed gravitational lensing within several galaxy clusters is higher than that estimated through the standard lambda cold dark matter model by an order of magnitude. While general relativity works perfectly well in the present universe where the spacetime is almost flat, it should be enhanced to account for the pre-existing universal curvature. This study presents new enhanced field equations utilising Einstein–Hilbert action. The enhanced field equations are reduced to Einstein field equations in a flat universe.

scholarly journals Extended General Relativity for a Curved Universe

2020 ◽  
Author(s):  
Mohammed B. Al-Fadhli
Keyword(s):  
General Relativity ◽  
Positive Curvature ◽  
Boundary Term ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Microwave Background ◽  
Conformal Curvature ◽  
Curvature Term ◽  
Extended Field ◽  
Matter Energy

The recent Planck Legacy release revealed the presence of an enhanced lensing amplitude in the cosmic microwave background, which endorses the early universe positive curvature with a confidence level exceeding 99%. Although general relativity performs accurately in the present universe where spacetime is almost flat, the necessity of dark matter/energy and the lost boundary term might be signs of its incompleteness. Utilising Einstein–Hilbert action, I present extended field equations considering the pre-existing universal curvatures. The new extended field equations are inclusive of Einstein field equations in addition to the boundary term and the conformal curvature term contributions.

scholarly journals Extended General Relativity for a Curved Universe

2020 ◽  
Author(s):  
Mohammed B. Al-Fadhli
Keyword(s):  
General Relativity ◽  
Positive Curvature ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Microwave Background ◽  
Conformal Curvature ◽  
Present Universe ◽  
Extended Field ◽  
Hilbert Action ◽  
Matter Energy

The Planck Legacy recent release revealed the presence of an enhanced lensing amplitude in the cosmic microwave background, which endorses the early universe positive curvature with a confidence level greater than 99%. Although General Relativity performs accurately in the present universe where spacetime is almost flat, its lost boundary term and the need of dark matter/energy might indicate its incompleteness. By utilising the Einstein–Hilbert action, this letter presents new extended field equations considering pre-existing universal curvatures and boundary contributions. The extended field equations are inclusive of Einstein field equations in addition to the boundary and the conformal curvature terms, which could remove the singularities from the theory.

INFLATION AFTER WMAP

2011 ◽  
Vol 20 (08) ◽  
pp. 1471-1477
Author(s):  
KIN-WANG NG
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Microwave Background ◽  
Cold Dark Matter Model ◽  
Cosmic Microwave Background Anisotropy ◽  
Matter Model ◽  
Reflection Asymmetry ◽  
Dark Matter Model

Recent measurements of the large-scale cosmic microwave background anisotropy made by the Wilkinson Microwave Anisotropy Probe (WMAP) mission indicate a reflection asymmetry, an axis of evil, a low quadrupole, and a few multipoles deviated from predicted in the cold dark matter model with a cosmological constant. All of these may give us a hint about the physics of inflation during the first few e-folds or during the inflating period. Efforts taken along this direction will be reviewed and our recent work will be discussed.

scholarly journals Extended General Relativity for a Curved Universe

2021 ◽  
Author(s):  
Mohammed B. Al-Fadhli
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Early Universe ◽  
Cold Dark Matter ◽  
Positive Curvature ◽  
Boundary Term ◽  
Radius Of Curvature ◽  
Field Equations ◽  
Extended Field ◽  
Background Curvature

The recent Planck Legacy release revealed the presence of an enhanced lensing amplitude in the cosmic microwave background (CMB). Notably, this amplitude is higher than that estimated by the lambda cold dark matter model (ΛCDM), which endorses the positive curvature of the early Universe with a confidence level greater than 99%. Although General Relativity (GR) performs accurately in the local/present Universe where spacetime is almost flat, its lost boundary term, incompatibility with quantum mechanics and the necessity of dark matter and dark energy might indicate its incompleteness. By utilising the Einstein–Hilbert action, this study presents extended field equations considering the pre-existing/background curvature and the boundary contribution. The extended field equations consist of Einstein field equations with a conformal transformation feature in addition to the boundary term, which could remove singularities from the theory and facilitate its quantisation. The extended equations have been utilised to derive the evolution of the Universe with reference to the scale factor of the early Universe and its radius of curvature.

scholarly journals Resolving XENON excess with decaying cold dark matter

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Shuai Xu ◽  
Sibo Zheng
Keyword(s):  
Dark Matter ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Recoil Energy ◽  
Microwave Background ◽  
Signal Rate ◽  
Cold Dark Matter Model ◽  
Electron Recoil ◽  
Matter Model ◽  
Dark Matter Model

AbstractWe propose a decaying cold dark matter model to explain the excess of electron recoil observed at the XENON1T experiment. In this scenario, the daughter dark matter from the parent dark matter decay easily obtains velocity large enough to saturate the peak of the electron recoil energy around 2.5 keV, and the observed signal rate can be fulfilled by the parent dark matter with a mass of order 10–200 MeV and a lifetime larger than the age of Universe. We verify that this model is consistent with experimental limits from dark matter detections, Cosmic microwave background and large scale structure experiments.

scholarly journals Two Analytic Relations Connecting the Hot Gas Astrophysics with the Cold Dark Matter Model for Galaxy Clusters

2021 ◽  
Vol 923 (1) ◽  
pp. 95
Author(s):  
Man Ho Chan
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Gravitational Lensing ◽  
Cold Dark Matter ◽  
X Ray ◽  
Hot Gas ◽  
Cold Dark Matter Model ◽  
Matter Model ◽  
Analytical Relations ◽  
Dark Matter Model

Abstract Galaxy clusters are good targets for examining our understanding of cosmology. Apart from numerical simulations and gravitational lensing, X-ray observation is the most common and conventional way to analyze the gravitational structures of galaxy clusters. Therefore, it is valuable to have simple analytical relations that can connect the observed distribution of the hot, X-ray-emitting gas to the structure of the dark matter in the clusters as derived from simulations. In this article, we apply a simple framework that can analytically connect the hot gas empirical parameters with the standard parameters in the cosmological cold dark matter model. We have theoretically derived two important analytic relations, r s ≈ 3 r c and ρ s ≈ 9 β kT / 8 π Gm g r c 2 , which can easily relate the dark matter properties in galaxy clusters with the hot gas properties. This can give a consistent picture describing gravitational astrophysics for galaxy clusters by the hot gas and cold dark matter models.

scholarly journals Extended General Relativity for a Conformally Curved Universe

2021 ◽  
Author(s):  
Mohammed B. Al-Fadhli
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Cold Dark Matter ◽  
Power Spectra ◽  
Boundary Term ◽  
Field Equations ◽  
Microwave Background ◽  
Extended Field ◽  
Background Curvature ◽  
Invariance Theory

The recent Planck Legacy release confirmed the presence of an enhanced lensing amplitude in the cosmic microwave background (CMB) power spectra. Notably, this amplitude is higher than that estimated by the lambda cold dark matter model (ΛCDM), which endorses a positively curved early Universe with a confidence level greater than 99%. Although General Relativity (GR) performs accurately in the local/present Universe where spacetime is almost flat, its lost boundary term, incompatibility with Quantum Mechanics and the necessity of dark matter/energy could indicate its incompleteness. By utilising the Einstein–Hilbert action, this letter presents extended field equations by considering the pre-existing/background curvature and the boundary contribution. The extended field equations consist of Einstein field equations with a conformal transformation feature in addition to the boundary term, which can remove singularities, satisfy a conformal invariance theory and facilitate its quantisation.

scholarly journals Does general relativity highlight necessary connections in nature?

Synthese ◽  
2021 ◽  
Author(s):  
Antonio Vassallo
Keyword(s):  
General Relativity ◽  
Laws Of Nature ◽  
Coupling Mechanism ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Bianchi Identities ◽  
Physical Role ◽  
General Relativistic ◽  
Differential Relations ◽  
Necessary Connections

AbstractThe dynamics of general relativity is encoded in a set of ten differential equations, the so-called Einstein field equations. It is usually believed that Einstein’s equations represent a physical law describing the coupling of spacetime with material fields. However, just six of these equations actually describe the coupling mechanism: the remaining four represent a set of differential relations known as Bianchi identities. The paper discusses the physical role that the Bianchi identities play in general relativity, and investigates whether these identities—qua part of a physical law—highlight some kind of a posteriori necessity in a Kripkean sense. The inquiry shows that general relativistic physics has an interesting bearing on the debate about the metaphysics of the laws of nature.

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