73. P. T. Chrusciel, G. M. Greuel, R. Meinel, S. J. Szybka
The Ernst equation and ergosurfaces
Class. Quantum Grav., vol. 23, pp. 4399-4414 (2006).
[abstract] [preprint] [journal] |
Abstract:
We show that analytic solutions $\mcE$ of the Ernst equation with non-empty zero-level-set of $\Re \mcE$ lead to smooth ergosurfaces in space-time. In fact, the space-time metric is smooth near a "Ernst ergosurface" $E_f$ if and only if $\mcE$ is smooth near $E_f$ and does not have zeros of infinite order there. |
74. Leszek M. Sokołowski
Physical interpretation and viability of various metric nonlinear gravity theories
Proceedings of MG11 Meeting, Berlin, July 23-29, 2006 (2006).
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Abstract:
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75. L. Pysiak, M. Heller, Z. Odrzygóźdź, W. Sasin
Observables in a Noncommutative Approach to the Unification of Quanta and Gravity: A Finite Model
General Relativity and Gravitation, vol. 37, pp. 541-555 (2005).
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Abstract:
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76. Marek Demianski, Zdzislaw A. Golda, Andrzej Woszczyna
Evolution of density perturbations in a realistic universe
Gen. Rel. Grav., vol. 37, pp. 2063-2082 (2005).
[abstract] [preprint] [journal] |
Abstract:
Prompted by the recent more precise determination of the basic cosmological parameters and growing evidence that the matter-energy content of the universe is now dominated by dark energy and dark matter we present the general solution of the equation that describes the evolution of density perturbations in the linear approximation. It turns out that as in the standard CDM model the density perturbations grow very slowly during the radiation dominated epoch and their amplitude increases by a factor of about 4000 in the matter and later dark energy dominated epoch of expansion of the universe.
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77. Marek Szydlowski, Adam Krawiec, Wojciech Czaja
Phantom cosmology as a simple model with dynamical complexity
Phys. Rev., vol. E72, p. 036221 (2005).
[abstract] [preprint] [journal] |
Abstract:
We study the Friedman-Robertson-Walker model with phantom fields modeled in terms of scalar fields. We apply the Ziglin theory of integrability and find that the flat model is nonintegrable. Then we cannot expect to determine simple analytical solutions of the Einstein equations. We demonstrate that there is only a discrete set of parameters where this model is integrable. For comparison we describe the phantoms fields in terms of the barotropic equation of state. It is shown that in contrast to the phantoms modeled as scalar fields, the dynamics is always integrable and phase portraits are contracted. In this case we find the duality relation. |
78. Marek Szydlowski, Wojciech Czaja
Modified Friedmann cosmologies -Theory and observations
Annals Phys. , vol. 320, pp. 261-281 (2005).
[abstract] [preprint] [journal] |
Abstract:
This paper shows the results of the investigation of a class of Cardassian scenarios of the evolution of the universe in the formulation of the qualitative theory of dynamical systems. That theory allowed us to analyze all solutions for all possible initial conditions on the phase plane. In the Cardassian models we find that big-rip singularities are present as a typical behavior in the future if $n < 0$. We were also able to find some exact solution for the flat Cardassian models as well as a duality relation. In turn for the statistical analysis of SNIa data, without any priors on the matter content in the model, we obtain that the big-rip scenario is favored. The potential function for the Hamiltonian description of dynamics was reconstructed from the SNIa data (inverse dynamical problem). |
