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arXiv 1910.013512019-10-03gr-qc

On the uniqueness of a shear-vorticity-acceleration-free velocity field in space-times

Luca Guido Molinari, Adriano Tacchini, Carlo Alberto Mantica

备注：: 11 pages
发表信息：: General Relativity and Gravitation (2019) 51:127
DOI：: 10.1007/s10714-019-2607-1

英文摘要：

We prove that in space-times a velocity field that is shear, vorticity and acceleration-free, if any, is unique up to reflection, with these exceptions: generalized Robertson-Walker space-times whose space sub-manifold is warped, and twisted space-times (the scale function is space-time dependent) whose space sub-manifold is doubly twisted. In space-time dimension n = 4, the Ricci and the Weyl tensors are specified, and the Einstein equations yield a mixture of two perfect fluids.

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