Statistics – Computation
Scientific paper
Aug 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt.......102m&link_type=abstract
PhD Thesis, Centro Brasileiro de Pesquisas Físicas, RJ, Brazil, 2001.
Statistics
Computation
12
Scientific paper
We present a detailed study of a class of approximations to investigate the nonlinear evolution of large-scale tructures. In these approximations some dynamical quantities are determined locally in terms of the initial conditions. This makes them particularly useful in several applications, such as the determination of general features of the nonlinear evolution, or the computation of the mass function. Our analysis includes all the four local approximations that have been introduced in the literature and that are exact in spherical, cylindrical and plannar symmetries. We have investigated general properties of these approximations, their asymptotic limit and the collapse time with general initial conditions. We have verified that the behavior of these four approximations is very similar. It is shown that they reproduce very accurately the evolution of a homogeneous ellipsoid, they are exact in the linear regime and predict the correct value for the density contrast at second order. We noticed that in these approximations the collapse time decreases asymptotically with the inverse of the shear strength and is not very sensitive to the intermediate component of the initial shear. We have compared the perturbative result of the local approximations against the Lagrangian Perturbation Theory in the case of an ellipsoid. It is shown that one of these approximations is exact, at least up to third order, in this case. We have calculated the mass function of cosmic structures in these approximations. The results are compared with the Press & Schechter formula and the outcome of N-body simulations. We have shown that it is not possible to recover the positions of the volume elements in the local approximations. However it is still possible to compare the results with the N-body simulations and the observational data. We propose a method to do such a comparison. We have also investigated the variational formalism for relativistic fluid dynamics in view of its applications to practical situations. We have applied the variational principle to spherically symmetric configurations in general relativity and derived the equations of motion for the gravitational collapse. We have determined the effective action for a relativistic fluid in the weak-field limit. This formulation allows the derivation of effective equations of motion for a given Ansatz to the density profile.
No associations
LandOfFree
Gravitational Dynamics of Structure Fromation in the Universe does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Gravitational Dynamics of Structure Fromation in the Universe, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gravitational Dynamics of Structure Fromation in the Universe will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-819314