
doi: 10.1007/bf01645493
The Einstein tensors of metrics having a 3-parameter group of (global) isometries with 2-dimensional non-null orbitsG3(2,s/t) are studied in order to obtainalgebraic conditions guaranteeing an additional normal Killing vector. It is shown that Einstein spaces withG3(2,s/t) allow aG4. A critical review of some of the literature on Birkhoff's theorem and its generalizations is given.
83.53, structure of matter
83.53, structure of matter
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