6,854 research outputs found
Addendum: Symmetries of the energy-momentum tensor
In recent papers [1-3], we have discussed matter symmetries of non-static
spherically symmetric spacetimes, static plane symmetric spacetimes and
cylindrically symmetric static spacetimes. These have been classified for both
cases when the energy-momentum tensor is non-degenerate and also when it is
degenerate. Here we add up some consequences and the missing references about
the Ricci tensor.Comment: 7 pages, no figure, LaTe
Symmetries of Locally Rotationally Symmetric Models
Matter collineations of locally rotationally symmetric spacetimes are
considered. These are investigated when the energy-momentum tensor is
degenerate. We know that the degenerate case provides infinite dimensional
matter collineations in most of the cases. However, an interesting case arises
where we obtain proper matter collineations. We also solve the constraint
equations for a particular case to obtain some cosmological models.Comment: 12 pages, accepted for publication in Int. J. of Mod. Phys.
Classification of Static Plane Symmetric Spacetimes according to their Matter Collineations
In this paper we classify static plane symmetric spacetimes according to
their matter collineations. These have been studied for both cases when the
energy-momentum tensor is non-degenerate and also when it is degenerate. It
turns out that the non-degenerate case yields either {\it four}, {\it five},
{\it six}, {\it seven} or {\it ten} independent matter collineations in which
{\it four} are isometries and the rest are proper. There exists three
interesting cases where the energy-momentum tensor is degenerate but the group
of matter collineations is finite-dimensional. The matter collineations in
these cases are either {\it four}, {\it six} or {\it tenComment: 15 pages, LaTex, no figure
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