Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lightlike hypersurfaces on manifolds endowed with a conformal structure
  of Lorentzian signature   The authors study the geometry of lightlike hypersurfaces on manifolds $(M,
c)$ endowed with a pseudoconformal structure $c = CO (n - 1, 1)$ of Lorentzian
signature. Such hypersurfaces are of interest in general relativity since they
can be models of different types of physical horizons. On a lightlike
hypersurface, the authors consider the fibration of isotropic geodesics and
investigate their singular points and singular submanifolds. They construct a
conformally invariant normalization of a lightlike hypersurface intrinsically
connected with its geometry and investigate affine connections induced by this
normalization. The authors also consider special classes of lightlike
hypersurfaces. In particular, they investigate lightlike hypersurfaces for
which the elements of the constructed normalization are integrable.

5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex