Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superstring Scattering from O-planes   We write the vertex operators of massless NS-NS and RR states of Type II
superstring theory in the presence of Orientifold p-planes. They include the
usual vertex operators of Type II theory and their images. We then calculate
the two-point functions of these vertex operators at the projective plane PR_2
level. We show that the result can be written in the Veneziano-type formulae,
with the same kinematic factor that appears in the D_p-branes amplitudes. While
the scattering amplitudes with the usual vertex operators are not gauge
invariant, the above amplitudes are invariant. From the amplitude describing
scattering of two NS-NS states off the O-plane, we find the low energy
effective action of O-planes. The result shows a relative factor 2^{p-6}
between couplings to O-planes and to D-branes at (\alpha')^2 order.

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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: dg-ga