A new approach for doing theoretical and numeric work with Lemaitre-Tolman-Bondi dust models - General Relativity and Quantum CosmologyReport as inadecuate




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Abstract: We introduce quasi-local integral scalar variables for the study ofspherically symmetric Lemaitre-Tolman-Bondi LTB dust models. Besidesproviding a covariant, and theoretically appealing, interpretation for theparameters of these models, these variables allow us to study their dynamicsin their full generality by means of fluid flow evolution equations that canbe handled with simple numerical techniques and has a significant potential forastrophysical and cosmological applications. These evolution equations can alsobe understood in the framework of a gauge invariant and covariant formalism ofspherical non-linear perturbations on a FLRW background. The covariant timesplitting associated with the new variables leads, in a natural way, torephrase the known analytic solutions within an initial value framework inwhich covariant scalars are given by simple scaling laws. By using thisre-parametrization of the analytic solutions, we re-examine and provide analternative outlook to various theoretical issues already treated in theliterature: regularity conditions, an Omega parameter, as well as the fittingof a given LTB model to radial profiles of density or velocity at differentcosmic times. Other theoretical issues and numeric applications will beexamined in separate articles.



Author: Roberto A Sussman

Source: https://arxiv.org/







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