Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Noncommutativity and Its Freedoms Due to the PP-Wave and Background
  Gauge Fields   In this article we consider an open string attached to a D$_p$-brane, in the
presence of the pp-wave and background gauge fields. The effects of the string
mass on the open string propagator, open string metric and the noncommutativity
parameter are studied. Some free matrices appear in the propagator and in the
open string variables. The symmetries of the string propagator and consistency
with the zero mass case put some restrictions on these matrices.

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The categories of this paper are: supr-con
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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: eess
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
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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: q-fin
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph