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1
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New results in the use of a “reverse engineering” method in cosmologies with scalar field

100%
Vulcanov D.
Open Physics
|
2008
|
vol. 6
|
issue 1
84-96
EN
The method of “reverse engineering” for designing potentials in cosmologies with “quintessence” scalar field is systematically used for several types of cosmologies (through the time behavior of the scale factor). The general recipe is introduced and then applied when matter other than the scalar field is present, and for tachyonic scalar fields. The possibility of using this method for prescribing initial data in numerical simulations in cosmology is investigated.
2
Content available remote

Extreme gravitational lensing in vicinity of Schwarzschild-de Sitter black holes

88%
Bakala P., Čermák P., Hledík S., Stuchlík Z., Truparová K.
Open Physics
|
2007
|
vol. 5
|
issue 4
599-610
EN
We have developed a realistic, fully general relativistic computer code to simulate optical projection in a strong, spherically symmetric gravitational field. The standard theoretical analysis of optical projection for an observer in the vicinity of a Schwarzschild black hole is extended to black hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de Sitterspacetimes. Influence of the cosmological constant is investigated for static observers and observers radially free-falling from the static radius. Simulations include effects of the gravitational lensing, multiple images, Doppler and gravitational frequency shift, as well as the intensity amplification. The code generates images of the sky for the static observer and a movie simulations of the changing sky for the radially free-falling observer. Techniques of parallel programming are applied to get a high performance and a fast run of the BHC simulation code.
3
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Relativistic perihelion precession of orbits of Venus and the Earth

75%
Biswas A., Mani K.
Open Physics
|
2008
|
vol. 6
|
issue 3
754-758
EN
Among all the theories proposed to explain the “anomalous” perihelion precession of Mercury’s orbit first announced in 1859 by Le Verrier, the general theory of relativity proposed by Einstein in November 1915 alone could calculate Mercury’s “anomalous” precession with the precision demanded by observational accuracy. Since Mercury’s precession was a directly derived result of the full general theory, it was viewed by Einstein as the most critical test of general relativity from amongst the three tests he proposed. With the advent of the space age, the level of observational accuracy has improved further and it is now possible to detect this precession for other planetary orbits of the solar system - viz., Venus and the Earth. This conclusively proved that the phenomenon of “anomalous” perihelion precession of planetary orbits is a relativistic effect. Our previous papers presented the mathematical model and the computed value of the relativistic perihelion precession of Mercury’s orbit using an alternate relativistic gravitational model, which is a remodeled form of Einstein’s relativity theories, and which retained only experimentally proven principles. In addition this model has the benefit of data from almost a century of relativity experimentation, including those that have become possible with the advent of the space age. Using this model, we present in this paper the computed values of the relativistic precession of Venus and the Earth, which compare well with the predictions of general relativity and are also in agreement with the observed values within the range of uncertainty.
4
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Simulation model for shapiro time delay and light deflection experiments

75%
Biswas A., Mani K.
Open Physics
|
2004
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vol. 2
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issue 4
687-697
EN
The time delay experiment proposed by I.I. Shapiro in 1964 and conducted in the seventies was the most precise experiment of general relativity until that time. Further experimentation has improved the accuracy level of both the time delay and the light deflection experiments. A simulation model is proposed that involves only a simple mass and time transformation factor involving velocity of light. The light deflection and the time delay experiments are numerically simulated using this model that does not use the general relativistic equations. The computed values presented in this paper compare well with recent levels of accuracy of their respective experimental results.
5
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Simulation model for anomalous precession of the perihelion of mercury's orbit

75%
Biswas A., Mani K.
Open Physics
|
2005
|
vol. 3
|
issue 1
69-76
EN
The ‘anomalous perihelion precession’ of Mercury, announced by Le Verrier in 1859, was a highly controversial topic for more than half a century and invoked many alternative theories until 1916, when Einstein presented his theory of general relativity as an alternative theory of gravitation and showed perihelion precession to be one of its potential manifestations. As perihelion precession was a directly derived result of the full General Theory and not just the Equivalence Principle, Einstein viewed it as the most critical test of his theory. This paper presents the computed value of the anomalous perihelion precession of Mercury's orbit using a new relativistic simulation model that employs a simple transformation factor for mass and time, proposed in an earlier paper. This computed value compares well with the prediction of general relativity and is, also, in complete agreement with the observed value within its range of uncertainty. No general relativistic equations have been used for computing the results presented in this paper.
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