Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mixed type surfaces with bounded Gaussian curvature in three-dimensional
  Lorentzian manifolds   A mixed type surface is a connected regular surface in a Lorentzian
3-manifold with non-empty spacelike and timelike point sets. The induced metric
of a mixed type surface is a signature-changing metric, and their lightlike
points may be regarded as singular points of such metrics. In this paper, we
investigate the behavior of Gaussian curvature at a non-degenerate lightlike
point of a mixed type surface. To characterize the boundedness of Gaussian
curvature at a non-degenerate lightlike points, we introduce several
fundamental invariants along non-degenerate lightlike points, such as the
lightlike singular curvature and the lightlike normal curvature. Moreover,
using the results by Pelletier and Steller, we obtain the Gauss-Bonnet type
formula for mixed type surfaces with bounded Gaussian curvature.

20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg