arXiv subjects

J. -M. Alimi

Publications and source records attributed to J. -M. Alimi.

21 records · Page 2Linked to original sources

arXiv1999

Asymptotic and Exact Solutions of Perfect-Fluid Scalar-Tensor Cosmologies

We present a method which enables exact solutions to be found for at homogeneous and isotropic scalar-tensor cosmologies with an arbitrary $ω(Φ)$ function and satisfying the general perfect fluid state equation $P=(γ-1)ρc^2$. This method has been used to analyze a wide range of asymptotic analytical solutions at early and late times for different epochs in the cosmic history: false vacuum inflationary models, vacuum and radiation-dominated models, and matter-dominated models. We also describe the qualitative behavior of models at intermediary times and give exact solutions at any time for some particular scalar-tensor theories.

astro-ph↗

arXiv1999

Stability of rotating spherical stellar systems

We study the stability of rotating collisionless self-gravitating spherical systems by using high resolution N-body experiments on a Connection Machine CM-5. We added rotation to Ossipkov-Merritt (hereafter OM) anisotropic spherical systems by using two methods. The first method conserves the anisotropy of the distribution function defined in the OM algorithm. The second method distorts the systems in velocity space. We then show that the stability of systems depends both on their anisotropy and on the value of the ratio between the total kinetic energy and the rotational kinetic energy. We also test the relevance of the stability parameters introduced by Perez et al. (1996) for the case of rotating systems.

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arXiv1995

A Morphological Indicator for Comparing Simulated Cosmological Scenarios with Observations

We propose a morphological multi-scale analysis of large-scale structures obtained by computer simulations and by observations. Structures are obtained at different scales by applying a wavelet transform on the observed and simulated data. Application of a segmentation algorithm allows a quantitative morphological description of the structures at each scale. The morphological parameter which we propose represents the deviation of a structure from sphericity. The dependence on scale of this simple parameter is shown to characterize in simulations the underlying cosmological model. We compare the HDM, CDM and mixed models with the CfA catalogue. This comparison favours a mixed model containing $65\%$ of CDM, $30\%$ of HDM, and $5\%$ baryonic matter.

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