Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Marstrand Theorem in Nonpositive Curvature   In a paper from 1954, Marstrand proved that if $K\subset \mathbb{R}^2$ with
Hausdorff dimension greater than 1, then its one-dimensional projection has
positive Lebesgue measure for almost-all directions. In this article, we show
that if $M$ is a simply connected surface with non-positive curvature, then
Marstrand's theorem is still valid.

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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: q-bio
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The categories of this paper are: cond-mat
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The categories of this paper are: physics
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: hep-ph