2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/109879This paper has been withdrawn by the author due to an error in the use of the Cauchy-Kowalevski theorem in section 4., theorem 4.1 which does not allow to prove the final result. When (and if) this error will be cured it will be replaced by a corrected version of the result.This paper has been withdrawnGeneral Relativity and Quantum Cosmologytext