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# Asian Journal of Mathematics

## Volume 17 (2013)

### Number 4

### Spacelike foliations by $(n - 1)$-umbilical hypersurfaces in spacetimes

Pages: 621 – 644

DOI: http://dx.doi.org/10.4310/AJM.2013.v17.n4.a5

#### Authors

#### Abstract

We consider the problem of whether a given spacetime admits a foliation by $(n - 1)$-umbilical spacelike hypersurfaces. We introduce the notion of a timelike closed partially conformal vector field in a spacetime and show that the existence of a vector field of this kind guarantees in turn the existence of that foliation. We then construct explicit examples of families of $(n - 1)$-umbilical spacelike hypersurfaces in the de Sitter space. Imposing the further condition of having constant $r$-th mean curvature, we give the complete description of any leaf of a foliation of the de Sitter space by these hypersurfaces. Finally, in a spacetime foliated by $(n - 1)$-umbilical spacelike hypersurfaces we characterize the immersed spacelike hypersurfaces which are $(n - 1)$-umbilical.

#### Keywords

closed partially conformal vector field, $(n - 1)$-umbilical spacelike hypersurface

#### 2010 Mathematics Subject Classification

Primary 53C12. Secondary 53A10.