Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rigidity of Convex Surfaces in Homogeneous Spaces   We prove rigidity of oriented isometric immersions of complete surfaces in
the homo- geneous 3-manifolds E(k; {\tau}) (different from the space forms)
having the same positive extrinsic curvature.

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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
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The categories of this paper are: physics
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The categories of this paper are: q-alg
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The categories of this paper are: hep-th