Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The surface states of topological insulators - Dirac fermion in curved
  two dimensional spaces   The surface of a topological insulator is a closed two dimensional manifold.
The surface states are described by the Dirac Hamiltonian in curved two
dimensional spaces. For a slab-like sample with a magnetic field perpendicular
to its top and bottom surfaces, there are chiral states delocalized on the four
side faces. These "chiral sheets" carry both charge and spin currents. In
strong magnetic fields the quantized charge Hall effect ($\s_{xy}=(2n+1)e^2/h$)
will coexist with spin Hall effect.

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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom