%0 Journal Article
%T Investigation of all Ricci semi-symmetric and all conformally semi-symmetric spacetimes
%A Jan E. £żman
%J Mathematics
%D 2010
%I arXiv
%R 10.1088/1742-6596/314/1/012020
%X We find all Ricci semi-symmetric as well as all conformally semi-symmetric spacetimes. Neither of these properties implies the other. We verify that only conformally flat spacetimes can be Ricci semi-symmetric without being conformally semi-symmetric and show that only vacuum spacetimes and spacetimes with just a $\Lambda$-term can be Ricci semi-symmetric without being conformally semi-symmetric.
%U http://arxiv.org/abs/1006.5684v2