scholarly journals Gravitational coupling and the cosmological constant

2018 ◽  
Vol 27 (08) ◽  
pp. 1850086
Author(s):  
Yousef Bisabr
Keyword(s):  
Cosmological Constant ◽  
Equivalence Principle ◽  
Weak Equivalence ◽  
Gravitational Coupling ◽  
Dynamical Mechanism ◽  
Metric Tensor ◽  
Weak Equivalence Principle ◽  
Gravitational Model ◽  
Expansion Of The Universe ◽  
The Universe

We deal with a dynamical mechanism in which a large cosmological constant, as suggested by inflationary scenarios, decays due to expansion of the universe. This mechanism has its origin in the gravitational coupling of the vacuum density. We assume that the vacuum couples anomalously to gravity that is the metric tensor that appears the gravitational part is not the same as that appears the matter part as suggested by weak equivalence principle. Instead, the two metric tensors are taken to be conformally related. We show that this provides a dynamical mechanism which works during expansion of the universe. We also consider some observational consequences of such a gravitational model.

True dynamical tests of the weak equivalence principle for matter and anti-matter

2014 ◽  
Vol 30 ◽  
pp. 1460267 ◽  
Author(s):  
C. S. Unnikrishnan
Keyword(s):  
Equivalence Principle ◽  
Practical Importance ◽  
Weak Equivalence ◽  
Intrinsic Properties ◽  
General Belief ◽  
Weak Equivalence Principle ◽  
Quantum Numbers ◽  
Remarkable Result ◽  
Relativistic Kinetic Energy ◽  
The Universe

After a brief review of the evidence for the validity of the Weak Equivalence principle for anti-matter, I show that, contrary to general belief, the near equality of the Shapiro delay for photons, neutrinos and anti-neutrinos in the galactic gravitational potential is not a true test of the WEP for their intrinsic properties and quantum numbers due to the overwhelming contribution to the gravitational mass from the relativistic kinetic energy. Then I prove the remarkable result that particles that obey the Newtonian law of dynamics automatically respect the WEP due to the firm equivalence between the law of motion and the WEP in any relativistic scenario, through gravity of all the matter in the Universe. Thus a test of the validity of Newtons's law in any force field is a true test of the WEP and provides strong direct tests of WEP for anti-particles. This result opens up an entire new insight of conceptual and practical importance for the tests of WEP.

DELTA GRAVITY AND THE ACCELERATED EXPANSION OF THE UNIVERSE

2011 ◽  
Vol 20 (supp01) ◽  
pp. 65-72
Author(s):  
JORGE ALFARO
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Cosmological Constant ◽  
Equivalence Principle ◽  
Equations Of Motion ◽  
Accelerated Expansion ◽  
Symmetric Tensors ◽  
Test Particles ◽  
Expansion Of The Universe ◽  
The Universe

We study a model of the gravitational field based on two symmetric tensors. The equations of motion of test particles are derived. We explain how the Equivalence principle is recovered. Outside matter, the predictions of the model coincide exactly with General Relativity, so all classical tests are satisfied. In Cosmology, we get accelerated expansion without a cosmological constant.

scholarly journals Testing the weak equivalence principle

2009 ◽  
Vol 5 (S261) ◽  
pp. 390-401 ◽  
Author(s):  
Anna M. Nobili ◽  
Gian Luca Comandi ◽  
Raffaello Pegna ◽  
Donato Bramanti ◽  
Suresh Doravari ◽  
...  
Keyword(s):  
General Relativity ◽  
Equivalence Principle ◽  
Large Scale ◽  
Past History ◽  
Low Earth Orbit ◽  
Small Scale ◽  
Current View ◽  
Weak Equivalence ◽  
Weak Equivalence Principle ◽  
The Universe

AbstractThe discovery of Dark Energy and the fact that only about 5% of the mass of the universe can be explained on the basis of the current laws of physics have led to a serious impasse. Based on past history, physics might indeed be on the verge of major discoveries; but the challenge is enormous. The way to tackle it is twofold. On one side, scientists try to perform large scale direct observations and measurements – mostly from space. On the other, they multiply their efforts to put to the most stringent tests ever the physical theories underlying the current view of the physical world, from the very small to the very large. On the extremely small scale very exciting results are expected from one of the most impressive experiments in the history of mankind: the Large Hadron Collider. On the very large scale, the universe is dominated by gravity and the present impasse undoubtedly calls for more powerful tests of General Relativity – the best theory of gravity to date. Experiments testing the Weak Equivalence Principle, on which General Relativity ultimately lies, have the strongest probing power of them all; a breakthrough in sensitivity is possible with the “Galileo Galilei” (GG) satellite experiment to fly in low Earth orbit.

Cosmological constant

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Vacuum Fluctuations ◽  
Present Epoch ◽  
Modify Gravity ◽  
Expansion Of The Universe ◽  
The Universe

The contribution of vacuum fluctuations to the cosmological constant is reconsidered studying the dependence on the used regularisation scheme. Then alternative explanations for the observed accelerated expansion of the universe in the present epoch are introduced which either modify gravity or add a new component of matter, dubbed dark energy. The chapter closes with some comments on attempts to quantise gravity.

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 Testing the Weak Equivalence Principle Using Optical and Near-infrared Crab Pulses

2018 ◽  
Vol 861 (1) ◽  
pp. 66 ◽  
Author(s):  
Calvin Leung ◽  
Beili Hu ◽  
Sophia Harris ◽  
Amy Brown ◽  
Jason Gallicchio ◽  
...  
Keyword(s):  
Equivalence Principle ◽  
Near Infrared ◽  
Weak Equivalence ◽  
Weak Equivalence Principle

scholarly journals ANISOTROPIC COMPACT STARS WITH VARIABLE COSMOLOGICAL CONSTANT

2012 ◽  
Vol 21 (13) ◽  
pp. 1250088 ◽  
Author(s):  
SK. MONOWAR HOSSEIN ◽  
FAROOK RAHAMAN ◽  
JAYANTA NASKAR ◽  
MEHEDI KALAM ◽  
SAIBAL RAY
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Compact Star ◽  
Compact Stars ◽  
Radial Dependence ◽  
Regularity Conditions ◽  
Variable Cosmological Constant ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Surface Redshift

Recently, the small value of the cosmological constant and its ability to accelerate the expansion of the universe is of great interest. We discuss the possibility of forming of anisotropic compact stars from this cosmological constant as one of the competent candidates of dark energy. For this purpose, we consider the analytical solution of Krori and Barua metric. We take the radial dependence of cosmological constant and check all the regularity conditions, TOV equations, stability and surface redshift of the compact stars. It has been shown as conclusion that this model is valid for any compact star and we have cited 4U 1820-30 as a specific example of that kind of star.

Heuristic determination of the cosmological constant

2021 ◽  
pp. 2150114
Author(s):  
Manuel Urueña Palomo ◽  
Fernando Pérez Lara
Keyword(s):  
Field Theory ◽  
Energy Density ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Fundamental Constants ◽  
Quantum Field ◽  
Brute Force ◽  
Expansion Of The Universe ◽  
The Universe

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in physics performing a dimensional analysis, in search of an equation resulting in the measured energy density of the vacuum or cosmological constant that is assumed to cause the accelerated expansion of the universe.

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