Author: Rossella Piscopo

We prove that a non-trivial conformal Killing algebra with bidimensional orbits of a 4-dimensional pseudo-Riemannian manifold is isomorphic to the Rotondaro algebra either of dimension 3, or of 4. We also give an exact description of Ricci flat 4-metrics that admit a non-trivial Conformal Killing algebra with bidimensional orbits.

14 pages, LaTeX-2e.

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