منابع مشابه
Nonsingular Cosmologies from Branes
We analyse possible cosmological scenarios on a brane where the brane acts as a dy-namical boundary of various black holes with anti-de Sitter or de Sitter asymptotics. In many cases, the brane is found to describe completely non-singular universe. In some cases, quantum gravity era of the brane-universe can also be avoided by properly tuning bulk parameters. We further discuss the creation of ...
متن کاملAccelerating Cosmologies from S-Branes
We point out that the recently proposed model of a flat 4-dimensional universe with accelerated expansion in string/M-theory is a special case of time-dependent solutions that the author found under the name of “S-branes.” We also show that similar accelerating models can be obtained from S-branes if the internal space is chosen to be hyperbolic or flat spaces. PACS numbers: 04.50.+h, 11.25.Yb,...
متن کاملNonsingular multidimensional cosmologies with Lobachevsky spatial sections
Examples of nonsingular cosmological models are presented on the basis of exact solutions to multidimensional gravity equations. These examples involve pure imaginary scalar fields, or, in other terms, “phantom” fields with an unusual sign of the kinetic term in the Lagrangian. We show that, with such fields, hyperbolic nonsingular models with a cosmological bounce (unlike spherical and spatial...
متن کاملNonsingular multidimensional cosmologies without fine tuning
Exact cosmological solutions for effective actions in D dimensions inspired by the tree-level superstring action are studied. For a certain range of free parameters existing in the model, nonsingular bouncing solutions are found. Among them, of particular interest can be open hyperbolic models, in which, without any fine tuning, the internal scale factor and the dilaton field (connected with st...
متن کاملA note on accelerating cosmologies from compactifications and S-branes
We give a simple interpretation of the recent solutions for cosmologies with a transient accelerating phase obtained from compactification in hyperbolic manifolds, or from S-brane solutions of string/M-theory. In the four-dimensional picture, these solutions correspond to bouncing the radion field off its exponential potential. Acceleration occurs at the turning point, when the radion stops and...
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ژورنال
عنوان ژورنال: International Journal of Modern Physics A
سال: 2004
ISSN: 0217-751X,1793-656X
DOI: 10.1142/s0217751x04017513