scholarly journals THE NON-RELATIVISTIC LIMIT OF THE EULER–NORDSTRÖM SYSTEM WITH COSMOLOGICAL CONSTANT

2009 ◽  
Vol 21 (07) ◽  
pp. 821-876 ◽  
Author(s):  
JARED SPECK
Keyword(s):  
Sobolev Space ◽  
Cosmological Constant ◽  
Singular Limit ◽  
Poisson System ◽  
Speed Of Light ◽  
Relativistic Limit ◽  
Sobolev Estimates ◽  
Space Launch ◽  
The Family ◽  
Energy Currents

In this paper, we study the singular limit c → ∞ of the family of Euler–Nordström systems indexed by the parameters κ2 and c[Formula: see text], where κ2 > 0 is the cosmological constant and c is the speed of light. Using Christodoulou's techniques to generate energy currents, we develop Sobolev estimates that show initial data belonging to an appropriate Sobolev space launch unique solutions to the [Formula: see text] system that converge to corresponding unique solutions of the Euler–Poisson system with the cosmological constant κ2 as c tends to infinity.

scholarly journals Three-dimensional Maxwellian extended Newtonian gravity and flat limit

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Patrick Concha ◽  
Lucrezia Ravera ◽  
Evelyn Rodríguez ◽  
Gustavo Rubio
Keyword(s):  
Cosmological Constant ◽  
Three Dimensional ◽  
Expansion Method ◽  
Gravity Models ◽  
Newtonian Gravity ◽  
Newtonian Theory ◽  
Relativistic Limit ◽  
Expansion Procedure ◽  
Three Space ◽  
Chern Simons

Abstract In the present work we find novel Newtonian gravity models in three space-time dimensions. We first present a Maxwellian version of the extended Newtonian gravity, which is obtained as the non-relativistic limit of a particular U(1)-enlargement of an enhanced Maxwell Chern-Simons gravity. We show that the extended Newtonian gravity appears as a particular sub-case. Then, the introduction of a cosmological constant to the Maxwellian extended Newtonian theory is also explored. To this purpose, we consider the non-relativistic limit of an enlarged symmetry. An alternative method to obtain our results is presented by applying the semigroup expansion method to the enhanced Nappi-Witten algebra. The advantages of considering the Lie algebra expansion procedure is also discussed.

INFLATION, QUINTESSENCE PROBLEM AND VARYING SPEED OF LIGHT

2002 ◽  
Vol 17 (05) ◽  
pp. 295-302
Author(s):  
SUBENOY CHAKRABORTY
Keyword(s):  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Speed Of Light ◽  
Expansion Of The Universe ◽  
The Universe

In this paper it is shown that the present accelerated expansion of the Universe can be explained only by considering variation of the speed of light, without taking into account the cosmological constant or quintessence matter.

scholarly journals COSMOLOGICAL CONSTANT AND THE SPEED OF LIGHT

2001 ◽  
Vol 10 (01) ◽  
pp. 41-48 ◽  
Author(s):  
W. R. ESPÓSITO MIGUEL ◽  
J. G. PEREIRA
Keyword(s):  
Gravitational Field ◽  
Cosmological Constant ◽  
Electromagnetic Waves ◽  
Light Propagation ◽  
Wave Optics ◽  
Speed Of Light ◽  
Positive Cosmological Constant ◽  
Velocity Of Light ◽  
Refractive Medium ◽  
The Relationship

By exploring the relationship between the propagation of electromagnetic waves in a gravitational field and the light propagation in a refractive medium, it is shown that, in the presence of a positive cosmological constant, the velocity of light will be smaller than its special relativity value. Then, restricting again to the domain of validity of geometrical optics, the same result is obtained in the context of wave optics. It is argued that this phenomenon and the anisotropy in the velocity of light in a gravitational field are produced by the same mechanism.

scholarly journals A VARYING-e BRANE WORLD COSMOLOGY

2002 ◽  
Vol 17 (03) ◽  
pp. 175-184 ◽  
Author(s):  
DONAM YOUM
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Electric Charge ◽  
Brane World ◽  
Speed Of Light ◽  
Cosmological Constant Problem ◽  
System Of Units ◽  
Flatness Problem

We study a varying electric charge brane world cosmology in the RS2 model obtained from a varying-speed-of-light brane world cosmology by redefining the system of units. We elaborate conditions under which the flatness problem and the cosmological constant problem can be resolved by such cosmological model.

scholarly journals WELL-POSEDNESS FOR THE EULER–NORDSTRÖM SYSTEM WITH COSMOLOGICAL CONSTANT

2009 ◽  
Vol 06 (02) ◽  
pp. 313-358 ◽  
Author(s):  
JARED SPECK
Keyword(s):  
Cosmological Constant ◽  
Hyperbolic Systems ◽  
Compact Perturbation ◽  
Initial Value ◽  
Scalar Theory ◽  
Energy Principle ◽  
First Order ◽  
Energy Currents ◽  
Standard Energy ◽  
Well Posed

In this paper, the author considers the motion of a relativistic perfect fluid with self-interaction mediated by Nordström's scalar theory of gravity. The evolution of the fluid is determined by a quasilinear hyperbolic system of PDEs, and a cosmological constant is introduced in order to ensure the existence of nonzero constant solutions. Accordingly, the initial value problem for a compact perturbation of an infinitely extended quiet fluid is studied. Although the system is neither symmetric hyperbolic nor strictly hyperbolic, Christodoulou's constructive results on the existence of energy currents for equations derivable from a Lagrangian can be adapted to provide energy currents that can be used in place of the standard energy principle available for first-order symmetric hyperbolic systems. After providing such energy currents, the author uses them to prove that the Euler–Nordström system with a cosmological constant is well-posed in a suitable Sobolev space.

scholarly journals Singular limit for the magnetohydrodynamics of the damped wave type in the critical Fourier–Sobolev space

2021 ◽  
Vol 271 ◽  
pp. 414-446
Author(s):  
Tatsuya Matsui ◽  
Ryosuke Nakasato ◽  
Takayoshi Ogawa
Keyword(s):  
Sobolev Space ◽  
Singular Limit ◽  
Wave Type

scholarly journals Determining Evolution of Cosmological Constant, Gravitational Constant and Speed of Light Using Nonadiabatic Cosmological Model and LLR Findings

Galaxies ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 67
Author(s):  
Gupta
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Gravitational Constant ◽  
Friedmann Equation ◽  
Distance Modulus ◽  
Significant Finding ◽  
Speed Of Light ◽  
Lunar Laser Ranging ◽  
Data Set ◽  
Λcdm Model

We have shown that the Hubble constant H0 embodies the information about the evolutionary nature of the cosmological constant Λ, gravitational constant G, and the speed of light c. We have derived expressions for the time evolution of G/c2 (≡K) and dark energy density εΛ related to Λ by explicitly incorporating the nonadiabatic nature of the universe in the Friedmann equation. We have found (dK/dt)/K = 1.8H0 and, for redshift z, εΛ,z/εΛ,0 = 0.4+0.61+z-1.52. Since the two expressions are related, we believe that the time variation of K (and therefore that of G and c) is manifested as dark energy in cosmological models. When we include the null finding of the lunar laser ranging (LLR) for (dG/dt)/G and relax the constraint that c is constant in LLR measurements, we get (dG/dt)/G = 5.4H0 and (dc/dt)/c = 1.8H0. Further, when we adapt the standard ΛCDM model for the z dependency of εΛ rather than it being a constant, we obtain surprisingly good results fitting the SNe Ia redshift z vs distance modulus µ data. An even more significant finding is that the new ΛCDM model, when parameterized with low redshift data set (z < 0.5), yields a significantly better fit to the data sets at high redshifts (z > 0.5) than the standard ΛCDM model. Thus, the new model may be considered robust and reliable enough for predicting distances of radiation emitting extragalactic redshift sources for which luminosity distance measurement may be difficult, unreliable, or no longer possible.

scholarly journals ISCOs and OSCOs in the Presence of a Positive Cosmological Constant in Massive Gravity

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 278
Author(s):  
Ángel Rincón ◽  
Grigoris Panotopoulos ◽  
Ilídio Lopes ◽  
Norman Cruz
Keyword(s):  
Cosmological Constant ◽  
Globular Clusters ◽  
Massive Gravity ◽  
Radial Coordinate ◽  
De Sitter ◽  
Positive Cosmological Constant ◽  
Circular Orbits ◽  
Relativistic Limit ◽  
Positive Roots ◽  
The Impact

We study the impact of a non-vanishing (positive) cosmological constant on the innermost and outermost stable circular orbits (ISCOs and OSCOs, respectively) within massive gravity in four dimensions. The gravitational field generated by a point-like object within this theory is known, generalizing the usual Schwarzschild–de Sitter geometry of General Relativity. In the non-relativistic limit, the gravitational potential differs by the one corresponding to the Schwarzschild–de Sitter geometry by a term that is linear in the radial coordinate with some prefactor γ, which is the only free parameter. Starting from the geodesic equations for massive test particles and the corresponding effective potential, we obtain a polynomial of fifth order that allows us to compute the innermost and outermost stable circular orbits. Next, we numerically compute the real and positive roots of the polynomial for several different structures (from the hydrogen atom to stars and globular clusters to galaxies and galaxy clusters) considering three distinct values of the parameter γ, determined using physical considerations, such as galaxy rotation curves and orbital precession. Similarly to the Kottler spacetime, both ISCOs and OSCOs appear. Their astrophysical relevance as well as the comparison with the Kottler spacetime are briefly discussed.

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