Field Equation of Nonlocal Gravity

2017 ◽  
Author(s):  
Bahram Mashhoon
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Gravitational Field ◽  
Field Equation ◽  
Abelian Group ◽  
Gravitational Field Equation ◽  
Differential Field ◽  
Einstein's Equation ◽  
Future Theory ◽  
World Function

In extended general relativity (GR), Einstein’s field equation of GR can be expressed in terms of torsion and this leads to the teleparallel equivalent of GR, namely, GR||, which turns out to be the gauge theory of the Abelian group of spacetime translations. The structure of this theory resembles Maxwell’s electrodynamics. We use this analogy and the world function to develop a nonlocal GR|| via the introduction of a causal scalar constitutive kernel. It is possible to express the nonlocal gravitational field equation as modified Einstein’s equation. In this nonlocal gravity (NLG) theory, the gravitational field is local, but satisfies a partial integro-differential field equation. The field equation of NLG can be expressed as Einstein’s field equation with an extra source that has the interpretation of the effective dark matter. It is possible that the kernel of NLG, which is largely undetermined, could be derived from a more general future theory.

scholarly journals Modification of Gravitational Field Equation due to Invariance of Light Speed and New System of Universe Evolution

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jian Liang Yang
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Field Equation ◽  
Invariant Solution ◽  
Inertial Mass ◽  
Gravitational Field Equation ◽  
Light Speed ◽  
Planetary Orbits ◽  
Celestial Bodies ◽  
The Universe

We make a systematic examination of the basic theory of general relativity and reemphasize the meaning of coordinates. Firstly, we prove that Einsteinʼs gravitational field equation has the light speed invariant solution and black holes are not an inevitable prediction of general relativity. Second, we show that the coupling coefficient of the gravitational field equation is not unique and can be modified as 4 π G to replace the previous − 8 π G , distinguish gravitational mass from the inertial mass, and prove that dark matter and dark energy are not certain existence and the expansion and contraction of the universe are proven cyclic, and a new distance-redshift relation which is more practical is derived. After that, we show that galaxies and celestial bodies are formed by gradual growth rather than by the accumulation of existing matter and prove that new matter is generating gradually in the interior of celestial bodies. For example, the radius of the Earth increases by 0.5 mm every year, and its mass increases by 1.2 trillion tons. A more reasonable derivation of the precession of planetary orbits is given, and the evolution equation of planetary orbits in the expanding space-time is also given. In a word, an alive universe unfolds in front of readers and the current cosmological difficulties are given new interpretations.

scholarly journals Einstein-aether theory in Weyl integrable geometry

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Andronikos Paliathanasis ◽  
Genly Leon ◽  
John D. Barrow
Keyword(s):  
Gravitational Field ◽  
Field Equation ◽  
Scalar Field ◽  
Field Model ◽  
Affine Connection ◽  
Dynamical Evolution ◽  
Field Equations ◽  
Gravitational Field Equation ◽  
Gravitational Field Equations ◽  
Geometric Origin

AbstractWe study the Einstein-aether theory in Weyl integrable geometry. The scalar field which defines the Weyl affine connection is introduced in the gravitational field equation. We end up with an Einstein-aether scalar field model where the interaction between the scalar field and the aether field has a geometric origin. The scalar field plays a significant role in the evolution of the gravitational field equations. We focus our study on the case of homogeneous and isotropic background spacetimes and study their dynamical evolution for various cosmological models.

scholarly journals Gravitoelectromagnetism and stellar orbits in galaxies

2021 ◽  
pp. 2150102
Author(s):  
Viktor T. Toth
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Gravitational Field ◽  
Magnetic Force ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Observable Effect ◽  
Stellar Orbits ◽  
Gravitational Fields ◽  
The Impact

Beyond the Newtonian approximation, gravitational fields in general relativity can be described using a formalism known as gravitoelectromagnetism. In this formalism, a vector potential, the gravitomagnetic potential, arises as a result of moving masses, in strong analogy with the magnetic force due to moving charges in Maxwell’s theory. Gravitomagnetism can affect orbits in the gravitational field of a massive, rotating body. This raises the possibility that gravitomagnetism may serve as the dominant physics behind the anomalous rotation curves of spiral galaxies, eliminating the need for dark matter. In this essay, we methodically work out the magnitude of the gravitomagnetic equivalent of the Lorentz force and apply the result to the Milky Way. We find that the resulting contribution is too small to produce an observable effect on these orbits. We also investigate the impact of cosmological boundary conditions on the result and find that these, too, are negligible.

Linearized Nonlocal Gravity

2017 ◽  
Author(s):  
Bahram Mashhoon
Keyword(s):  
Exact Solution ◽  
Dark Matter ◽  
Gravitational Field ◽  
Field Equation ◽  
Gravitational Lensing ◽  
Modified Gravity ◽  
Trivial Solution ◽  
Minkowski Spacetime ◽  
Linear Regime ◽  
Simple Generalization

The only known exact solution of the field equation of nonlocal gravity (NLG) is the trivial solution involving Minkowski spacetime that indicates the absence of a gravitational field. Therefore, this chapter is devoted to a thorough examination of NLG in the linear approximation beyond Minkowski spacetime. Moreover, the solutions of the linearized field equation of NLG are discussed in detail. We adopt the view that the kernel of the theory must be determined from observation. In the Newtonian regime of NLG, we recover the phenomenological Tohline-Kuhn approach to modified gravity. A simple generalization of the Kuhn kernel leads to a three-parameter modified Newtonian force law that is always attractive. Gravitational lensing is discussed. It is shown that nonlocal gravity (NLG), with a characteristic galactic lengthscale of order 1 kpc, simulates dark matter in the linear regime while preserving causality.

scholarly journals Modifications of Gravity Via Differential Transformations of Field Variables

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 240 ◽  
Author(s):  
Anton Sheykin ◽  
Dmitry Solovyev ◽  
Vladimir Sukhanov ◽  
Sergey Paston
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
Lagrange Multipliers ◽  
Additional Term ◽  
Field Theories ◽  
Original Theory ◽  
Embedding Theory ◽  
Differential Field ◽  
Theories Of Gravity ◽  
Mimetic Gravity

We discuss field theories appearing as a result of applying field transformations with derivatives (differential field transformations, DFTs) to a known theory. We begin with some simple examples of DFTs to see the basic properties of the procedure. In this process, the dynamics of the theory might either change or be conserved. After that, we concentrate on the theories of gravity which appear as a result of various DFTs applied to general relativity, namely the mimetic gravity and Regge–Teitelboim embedding theory. We review the main results related to the extension of dynamics in these theories, as well as the possibility to write down the action of a theory after DFTs as the action of the original theory before DFTs plus an additional term. Such a term usually contains some constraints with Lagrange multipliers and can be interpreted as an action of additional matter, which might be of use in cosmological applications, e.g., for the explanation of the effects of dark matter.

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