Browsing by Author "Nayeri, Ali"

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Possible Newtonian interpretation of relativistic cosmological perturbation theory
(2015-03-11) Nayeri, Ali; Padmanabhan, T.
Cosmological perturbations with wavelengths smaller than Hubble radius can be handled in the context of Newtonian theory with very high accuracy. The application of this Newtonian approximation, however, is restricted to nonrelativistic matter and cannot be used for relativistic matter. Recently, by modifying the continuity equation, Lima, et. a!., extended the domain of applicability of Newtonian cosmology to radiation dominated phase. We adopted this continuity equation to re-examine linear cosmological perturbation theory for a two fluid universe with uniform pressure. We study the evolution equations for density contrasts and their validity in different epochs and on scales larger than Hubble radius and compare the results with the full relativistic approach. The comparison shows the high accuracy of this approximation.
Structure formation in the quasi-steady state cosmology : A toy model
(American Astronomical Society, 1999-11-01) Nayeri, Ali; Engineer, Sunu; Narlikar, J. V.
The problem of formation of large-scale structure is discussed within the framework of the quasi-steady state cosmology (QSSC). The primary process of creation of matter and the resulting dynamics of ejection of matter from regions of strong gravitational Ðelds play a key role. To understand their workings, a toy model is used, in which from a set of randomly distributed creation centers a new generation of centers is created as part of an iterative algorithm. It is shown that the system develops clusters and voids along with filamentary structure, within a few iterations. The two-point correlation function and density distribution function for these simulations are shown to reproduce the observed clustering of the large-scale structure in the real universe.
Structure formation in the Quasi-Steady state cosmology: A toy model
(2015-03-01) Nayeri, Ali; Engineer, Sunu; Narlikar, J.V.; Hoyle, F.
The problem of formation of large scale structure is discussed within the framework of the Quasi-Steady State Cosmology (QSSC) . The primary process of creation of matter and the resulting dynamics of ejection of matter from regions of strong gravitational fields plays a key role. To understand its working, a toy model is used, in which from a set of randomly distributed creation centres a new generation of centres is created as part of an iterative algorithm. It is shown that the system develops clusters and voids along with filamentary structure, within a few iterations. The two point correlation function and density distribution function for these simulations are shown to reproduce the observed clustering of the large scale structure in the real universe.