Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Solution to the Doublet-Triplet Splitting Problem in the Type IIB
  Supergravity   The doublet--triplet mass splitting problem is one of the most serious
problems in supersymmetric grand unified theories (GUTs). A class of models
based on a product gauge group, such as the SU(5)_{GUT} times U(3)_H or the
SU(5)_{GUT} times U(2)_H, realize naturally the desired mass splitting that is
protected by an unbroken R symmetry. It has been pointed out that various
features in the models suggest that these product-group unification models are
embedded in a supersymmetric brane world. We show an explicit construction of
those models in the supersymmetric brane world based on the Type IIB
supergravity in ten dimensions. We consider T^6/(Z_{12} times Z_2) orientifold
for the compactified six extra dimensions. We find that all of the particles
needed for the GUT-symmetry-breaking sector are obtained from the D-brane
fluctuations. The three families of quarks and leptons are introduced at an
orbifold singularity, although their origin remains unexplained. This paper
includes extensive discussion on anomaly cancellation in a given orbifold
geometry. Relation to the Type IIB string theory, realization of R symmetry as
a rotation of extra-dimensional space, and effective superpotential at low
energies are also discussed.

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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: cs
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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: supr-con
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin