Authors: D. Catalano Ferraioli and A. M. Vinogradov
Pseudo-Riemannian 4-metrics with bidimensional null Killing orbits are
studied. Both Lorentzian and Kleinian (or neutral) cases, are treated
simultaneously. Under the assumption that the distribution orthogonal to
the orbits is completely integrable a complete exact description of Ricci
flat metrics admitting a bidimensional nonabelian Killing algebra is found.
17 pages, AmS-LaTeX (LaTeX-2e).
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