On Lorentz manifolds with abundant isometries (Q1822782)

Taking into account some results obtained by the author in [Proc. Am. Math. Soc. 100, 329-334 (1987; Zbl 0621.53049)] and [Hokkaido Math. J. 15, 309-315 (1986; Zbl 0608.53057)], this paper shows that a simply connected n-dimensional Lorentz manifold admitting a connected n(n-1)/2- dimensional (resp. \((n-1)(n-2)/2+2\)-dimensional) isometry group with compact isotropy subgroup at every point for \(n\geq 4\) (resp. \(n\geq 6)\) must be isometric to a certain warped product manifold.