Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On maximal hypersurfaces in Lorentz manifolds admitting a parallel
  lightlike vector field   We study constant mean curvature spacelike hypersurfaces and in particular
maximal hypersurfaces immersed in pp-wave spacetimes satisfying the timelike
convergence condition. We prove the non-existence of compact spacelike
hypersurfaces whose constant mean curvature is non-zero and also that every
compact maximal hypersurface is totally geodesic. Moreover, we give an
extension of the classical Calabi-Bernstein theorem to this class of pp-wave
spacetimes.

26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph