Author: Michael Bächtold

We study Ricci flat 4-metrics of any signature under the assumption that they allow a Lie algebra of Killing fields with 2-dimensional orbits along which the metric degenerates and whose orthogonal distribution is not integrable. It turns out that locally there is a unique (up to a sign) metric which satisfies the conditions. This metric is of signature (++--) and, moreover, homogeneous possessing a 6-dimensional symmetry algebra.

12 pages, LaTeX-2e.

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