Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hall Conductivity for Charged Strings and Modified Spectrum-Generating
  Algebra   When open strings end with a charge q on a D2-brane, which involves constant
background magnetic field B perpendicular to the brane, we calculate the Hall
conductivity for these charged strings. We also construct the corresponding
spectrum-generating algebra, which assures that our system is ghost-free under
some conditions.

25
The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an