Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A New Class of Supersymmetric Orientifolds with D-Branes at Angles   We describe a new class of supersymmetric orientifolds which combine the
world-sheet parity transformation with a complex conjugation in the compact
directions. As an example, we investigate in detail the orientifold of the Z_3
toroidal orbifold in six and four dimensions. We demonstrate how the solution
to the tadpole cancellation conditions, the resulting gauge groups and the
massless spectra depend on the choice of the complex structures on the tori,
giving rise to a variety of inequivalent models. We also summarize the results
for the orientifolds of the Z_4, Z_6 and Z_6' orbifolds in four and six
dimensions.

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The categories of this paper are: alg-geom
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The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
0
The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an