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Carlos Castro - One of the best experts on this subject based on the ideXlab platform.
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Quaternionic-valued Gravitation in 8D ,G rand Unification and Finsler Geometry
2012Co-Authors: Carlos CastroAbstract:A unification model of 4D gravity and SU(3) × SU(2) × U( 1) Yang-Mills Theory is presented. It is obtained from a Kaluza-Klein compactification of 8D quaternionic gravity on an internal CP 2 = SU(3)/U (2) symmetric space. We proceed to explore the nonlinear connection A a (x, y) formalism used in Finsler geometry to show how ordinary gravity in D = 4 + 2 dimensions has enough degrees of freedom to encode a 4D Gravitational and SU(5) Yang-Mills Theory. This occurs when the internal two-dim space is a sphere S 2 .T his is an appealing result because SU(5) is one of the candidate GUT groups. We conclude by discussing how the nonlinear connection formalism of Finsler geometry provides an infinite hierarchical extension of the Standard Model within a six dimensional Gravitational Theory due to the embedding of SU(3) × SU(2) × U( 1) ⊂ SU(5) ⊂ SU(∞).
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on born s deformed reciprocal complex Gravitational Theory and noncommutative gravity
Physics Letters B, 2008Co-Authors: Carlos CastroAbstract:Abstract Born's reciprocal relativity in flat spacetimes is based on the principle of a maximal speed limit (speed of light) and a maximal proper force (which is also compatible with a maximal and minimal length duality) and where coordinates and momenta are unified on a single footing. We extend Born's Theory to the case of curved spacetimes and construct a deformed Born reciprocal general relativity Theory in curved spacetimes (without the need to introduce star products) as a local gauge Theory of the deformed Quaplectic group that is given by the semi-direct product of U ( 1 , 3 ) with the deformed (noncommutative) Weyl–Heisenberg group corresponding to noncommutative generators [ Z a , Z b ] ≠ 0 . The Hermitian metric is complex-valued with symmetric and nonsymmetric components and there are two different complex-valued Hermitian Ricci tensors R μ ν , S μ ν . The deformed Born's reciprocal Gravitational action linear in the Ricci scalars R , S with Torsion-squared terms and BF terms is presented. The plausible interpretation of Z μ = E μ a Z a as noncommuting p -brane background complex spacetime coordinates is discussed in the conclusion, where E μ a is the complex vielbein associated with the Hermitian metric G μ ν = g ( μ ν ) + i g [ μ ν ] = E μ a E ¯ ν b η a b . This could be one of the underlying reasons why string-Theory involves gravity.
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on born s deformed reciprocal complex Gravitational Theory and noncommutative gravity
2008Co-Authors: Carlos CastroAbstract:Born’s reciprocal relativity in flat spacetimes is based on the principle of a maximal speed limit (speed of light) and a maximal proper force (which is also compatible with a maximal and minimal length duality) and where coordinates and momenta are unified on a single footing. We extend Born’s Theory to the case of curved spacetimes and construct a deformed Born reciprocal general relativity Theory in curved spacetimes (without the need to introduce star products) as a local gauge Theory of the deformed Quaplectic group that is given by the semi-direct product of U(1, 3) with the deformed (noncommutative) Weyl-Heisenberg group corresponding to noncommutative generators [Za, Zb] 6= 0. The Hermitian metric is complex-valued with symmetric and nonsymmetric components and there are two different complex-valued Hermitian Ricci tensors Rμν ,Sμν . The deformed Born’s reciprocal Gravitational action linear in the Ricci scalars R,S with Torsion-squared terms and BF terms is presented. The plausible interpretation of Zμ = E a μ Za as noncommuting p-brane background complex spacetime coordinates is discussed in the conclusion, where E μ is the complex vielbein associated with the Hermitian metric Gμν = g(μν) + ig[μν] = E a μ Ē b ν ηab. This could be one of the underlying reasons why string-Theory involves gravity. Born’s reciprocal (”dual”) relativity [1] was proposed long ago based on the idea that coordinates and momenta should be unified on the same footing, and consequently, if there is a limiting speed (temporal derivative of the position coordinates) in Nature there should be a maximal force as well, since force is the temporal derivative of the momentum. A curved phase space case scenario has been analyzed by Brandt [2] within the context of the Finsler geometry of the 8D tangent bundle of spacetime where there is a limiting value to the proper acceleration and such that generalized 8D Gravitational equations reduce
Chen Xiang - One of the best experts on this subject based on the ideXlab platform.
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First experiment to test whether space-time is flat. II. Effects of orbit
International Journal of Theoretical Physics, 1995Co-Authors: Zhang Junhao, Chen XiangAbstract:The gyroscope in an orbiting satellite will be acted on by additional Gravitational fields due to the rotation of the earth and due to the orbital velocity of the satellite. According to special relativistic Gravitational Theory, we deduce ψ L (S) —the gyroscope's precession rate due to the orbital velocity—and ψ S (S) —the gyroscope's precession rate due to the earth's rotation in the polar orbit case. The results are ψ L (S) = (2/3)ψ L (G) , ψ S (S) = (3/2) cos β(1 - sin2δ cos2β)1/2ψ S (G) , where β and δ are the gyroscope's polar angles, and ψ L (G) and ψ S (G) are the geodetic and frame-dragging precession rates predicted by general relativity, respectively.
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Difference between special relativistic Gravitational Theory and general relativity: Weak field limit
International Journal of Theoretical Physics, 1991Co-Authors: Zhang Junhao, Chen XiangAbstract:In the case of weak fields, we compare the Gravitational fields and the dynamical equation of a particle deduced from special relativistic Gravitational Theory with the corresponding results deduced from general relativity. Then both Gravitational theories can be tested by experiments.
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Special Relativistic Gravitational Theory
International Journal of Theoretical Physics, 1990Co-Authors: Zhang Junhao, Chen XiangAbstract:Based on special relativity, we introduce a way to develop a new field Theory from (1) the relativistic property of the particle coupling coefficient with the field, and (2) the field due to a static point source. As an example, we discuss a Theory of electromagnetic and Gravitational fields. The results of this special relativistic Gravitational Theory for the redshift and the deflection of light are the same as those deduced from general relativity. The results of experiments on the planetary perihelion procession shift and on an additional “short-range gravity” are more favorable to the special relativistic Gravitational Theory than to general relativity. We put forward a new idea to test experimentally whether the equivalence principle of general relativity is correct.
J. W. Moffat - One of the best experts on this subject based on the ideXlab platform.
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modified gravitation Theory mog and the aligo gw190521 Gravitational wave event
arXiv: General Relativity and Quantum Cosmology, 2020Co-Authors: J. W. MoffatAbstract:A consequence of adopting a modified Gravitational Theory (MOG) for the aLIGO GW190521 Gravitational wave detection involving binary black hole sources is to fit the aLIGO strain and chirp data with lower mass, compact coalescing binary systems such as neutron star-neutron star (NS-NS), black hole - neutron star (BH-NS), and black hole-black hole (BH-BH) systems. In MOG BH - BH component masses can be smaller than the component masses $m_1=85M_\odot$ and $m_2=66M_\odot$ inferred from the aLIGO GW190521 Gravitational wave event. This reduces the mass of the final remnant mass $M_f=150M_\odot$ and allows the primary, secondary and final remnant masses of the black holes to be formed by conventional stellar collapse models.
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Gravitational Theory galaxy rotation curves and cosmology without dark matter
Journal of Cosmology and Astroparticle Physics, 2005Co-Authors: J. W. MoffatAbstract:Einstein gravity coupled to a massive skew symmetric field Fμνλ leads to an acceleration law that modifies the Newtonian law of attraction between particles. We use a framework of non-perturbative renormalization group equations as well as observational input to characterize special renormalization group trajectories to allow for the running of the effective Gravitational coupling G and the coupling of the skew field to matter. Strong renormalization effects occur at large and small momentum scales. The latter lead to an increase of Newton's constant at large galactic and cosmological distances. For weak fields a fit to the flat rotation curves of galaxies is obtained in terms of the mass (mass-to-light ratio M/L) of galaxies. The fits assume that the galaxies are not dominated by exotic dark matter and that the effective Gravitational constant G runs with the distance scale. The equations of motion for test particles yield predictions for the solar system and the binary pulsar PSR 1913+16 that agree with the observations. The Gravitational lensing of clusters of galaxies can be explained without exotic dark matter. A Friedmann–Lemaitre–Robertson–Walker cosmological model with an effective G = G(t) running with time can lead to consistent fits to cosmological data without assuming the existence of exotic cold dark matter.
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Dynamical Constraints in the Nonsymmetric Gravitational Theory
arXiv: General Relativity and Quantum Cosmology, 1996Co-Authors: J. W. MoffatAbstract:We impose in the nonsymmetric Gravitational Theory, by means of Lagrange multiplier fields in the action, a set of covariant constraints on the antisymmetric tensor field. The canonical Hamiltonian constraints in the weak field approximation for the antisymmetric sector yield a Hamiltonian energy bounded from below. An analysis of the Cauchy evolution, in terms of an expansion of the antisymmetric sector about a symmetric Einstein background, shows that arbitrarily small antisymmetric Cauchy data can lead to smooth evolution.
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Regularity theorems in the nonsymmetric Gravitational Theory
Journal of Mathematical Physics, 1995Co-Authors: J. W. MoffatAbstract:Regularity theorems are presented for cosmology and Gravitational collapse in non‐Riemannian Gravitational theories. These theorems establish conditions necessary to allow the existence of timelike and null path complete spacetimes for matter that satisfies the positive energy condition. Non‐Riemannian theories of gravity can have solutions that have a nonsingular beginning of the universe, and the Gravitational collapse of a star does not lead to a black hole event horizon and a singularity as a final stage of collapse. A perturbatively consistent version of nonsymmetric Gravitational Theory is studied that, in the long‐range approximation, has a static spherically symmetric solution which does not have black hole event horizons and has finite curvature invariants.
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Gravitational Waves in the Nonsymmetric Gravitational Theory
Physics Letters A, 1993Co-Authors: N. J. Cornish, J. W. Moffat, D. C. TatarskiAbstract:Abstract We prove that the flux of Gravitational radiation from an isolated source in the nonsymmetric Gravitational Theory is identical to that found in Einstein's general Theory of relativity.
Athanasios Prikas - One of the best experts on this subject based on the ideXlab platform.
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q stars in scalar-tensor Gravitational theories in extra dimensions
Journal of Mathematical Physics, 2006Co-Authors: Athanasios PrikasAbstract:We present Jordan-Brans-Dicke and general scalar-tensor Gravitational Theory in extra dimensions in an asymptotically flat or anti de Sitter spacetime. We consider a special gravitating, boson field configuration, a q star, in three, four, five, and six dimensions, within the framework of the above Gravitational Theory, and find that the parameters of the stable stars are a few percent different from the case of General Relativity.
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Q-stars in scalar–tensor Gravitational theories
Physics Letters B, 2005Co-Authors: Athanasios PrikasAbstract:Abstract We study q-stars in Brans–Dicke Gravitational Theory. We find that when the Brans–Dicke constant, ω BD , tends to infinity, the results of general relativity are reproduced. For other values of ω BD , the particle number, mass and radius of the star and the absolute value of the matter field are a few percent larger than in the case of general relativity. We also investigate the general scalar–tensor Gravitational Theory and find that the star parameters are a few percent larger than in the case of general relativity.
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Q-stars in scalar–tensor Gravitational theories
Physics Letters B, 2005Co-Authors: Athanasios PrikasAbstract:We study q-stars in Brans-Dicke Gravitational Theory. We find that when the Brans-Dicke constant, $\omega_{\textrm{BD}}$, tends to infinity, the results of General Relativity are reproduced. For other values of $\omega_{\textrm{BD}}$, the particle number, mass and radius of the star and the absolute value of the matter field are a few percent larger than in the case of General Relativity. We also investigate the general scalar-tensor Gravitational Theory and find that the star parameters are a few percent larger than in the case of General Relativity.Comment: 14 pages, to appear in Phys. Lett.
Zhang Junhao - One of the best experts on this subject based on the ideXlab platform.
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First experiment to test whether space-time is flat. II. Effects of orbit
International Journal of Theoretical Physics, 1995Co-Authors: Zhang Junhao, Chen XiangAbstract:The gyroscope in an orbiting satellite will be acted on by additional Gravitational fields due to the rotation of the earth and due to the orbital velocity of the satellite. According to special relativistic Gravitational Theory, we deduce ψ L (S) —the gyroscope's precession rate due to the orbital velocity—and ψ S (S) —the gyroscope's precession rate due to the earth's rotation in the polar orbit case. The results are ψ L (S) = (2/3)ψ L (G) , ψ S (S) = (3/2) cos β(1 - sin2δ cos2β)1/2ψ S (G) , where β and δ are the gyroscope's polar angles, and ψ L (G) and ψ S (G) are the geodetic and frame-dragging precession rates predicted by general relativity, respectively.
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Difference between special relativistic Gravitational Theory and general relativity: Weak field limit
International Journal of Theoretical Physics, 1991Co-Authors: Zhang Junhao, Chen XiangAbstract:In the case of weak fields, we compare the Gravitational fields and the dynamical equation of a particle deduced from special relativistic Gravitational Theory with the corresponding results deduced from general relativity. Then both Gravitational theories can be tested by experiments.
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Special Relativistic Gravitational Theory
International Journal of Theoretical Physics, 1990Co-Authors: Zhang Junhao, Chen XiangAbstract:Based on special relativity, we introduce a way to develop a new field Theory from (1) the relativistic property of the particle coupling coefficient with the field, and (2) the field due to a static point source. As an example, we discuss a Theory of electromagnetic and Gravitational fields. The results of this special relativistic Gravitational Theory for the redshift and the deflection of light are the same as those deduced from general relativity. The results of experiments on the planetary perihelion procession shift and on an additional “short-range gravity” are more favorable to the special relativistic Gravitational Theory than to general relativity. We put forward a new idea to test experimentally whether the equivalence principle of general relativity is correct.
