Theorems on shear-free perfect fluids with their Newtonian analogues
نویسنده
چکیده
In this paper we provide fully covariant proofs of some theorems on shearfree perfect fluids. In particular, we explicitly show that any shear-free perfect fluid with the acceleration proportional to the vorticity vector (including the simpler case of vanishing acceleration) must be either non-expanding or non-rotating. We also show that these results are not necessarily true in the Newtonian case, and present an explicit comparison of shear-free dust in Newtonian and relativistic theories in order to see where and why the differences appear. PACS: 04.20.-q, 04.20.Jb, 04.40.Nr, 98.80.Hw
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