Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Four-dimensional String Compactifications with D-Branes, Orientifolds
  and Fluxes   This review article provides a pedagogical introduction into various classes
of chiral string compactifications to four dimensions with D-branes and fluxes.
The main concern is to provide all necessary technical tools to explicitly
construct four-dimensional orientifold vacua, with the final aim to come as
close as possible to the supersymmetric Standard Model. Furthermore, we outline
the available methods to derive the resulting four-dimensional effective
action. Finally, we summarize recent attempts to address the string vacuum
problem via the statistical approach to D-brane models.

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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: funct-an
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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: chem-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: math
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: stat