科研之友
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摘要
We consider the space-like D p brane solutions of type II string theories having isometries ISO(p + 1) x SO(8 - p, 1). These are asymptotically flat solutions or in other words, the metrics become flat at the time scale tau >> tau(0). On the other hand, when tau similar to tau(0), we get (p + 1) + 1 dimensional flat FLRW metrics upon compactification on a (8 - p) dimensional hyperbolic space with time dependent radii. We show that the resultant (p + 1)+ 1 dimensional metrics describe transient accelerating cosmologies for all p from 1 to 6, i.e., from (2 + 1) to (7 + 1) space-time dimensions. We show how the accelerating phase changes with the interplay of the various parameters characterizing the solutions in (3 + 1) dimensions. Finally, for tau >> tau(0), after compactification on (8 - p) dimensional hyperbolic space, the resultant metrics are shown to take the form of (p + 1) + 1 dimensional de Sitter spaces upto a conformal transformation. Cosmologies here are decelerating, but, only in a particular conformal frame we get eternal acceleration.
- 出版日期2015-2-3
