**DIPS 12/2001**[tex source, PostScript, PDF file, dvi]-
**Title:**GRAVITATIONAL FIELDS WITH A NON ABELIAN BIDIMENSIONAL LIE ALGEBRA OF SYMMETRIES

**Authors:**G. Sparano, G. Vilasi, A. M. VinogradovVacuum gravitational fields invariant for a bidimensional non Abelian Lie algebra of Killing fields, are explicitly described. They are parameterized either by solutions of a transcendental equation (the

*tortoise equation*) or by solutions of a linear second order differential equation on the plane. Gravitational fields determined*via*the tortoise equation, are invariant for a 3-dimensional Lie algebra of Killing fields with bidimensional leaves. Global gravitational fields out of local ones are also constructed.

7 pages, LaTeX-2e.

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