Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An invariant theory of marginally trapped surfaces in the
  four-dimensional Minkowski space   A marginally trapped surface in the four-dimensional Minkowski space is a
spacelike surface whose mean curvature vector is lightlike at each point. We
associate a geometrically determined moving frame field to such a surface and
using the derivative formulas for this frame field we obtain seven invariant
functions. Our main theorem states that these seven invariants determine the
surface up to a motion in Minkowski space.
  We introduce meridian surfaces as one-parameter systems of meridians of a
rotational hypersurface in the four-dimensional Minkowski space. We find all
marginally trapped meridian surfaces.

34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an