Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: D-branes in Nongeometric Backgrounds   "T-fold" backgrounds are generically-nongeometric compactifications of string
theory, described by T^n fibrations over a base N with transition functions in
the perturbative T-duality group. We review Hull's doubled torus formalism,
which geometrizes these backgrounds, and use the formalism to constrain the
D-brane spectrum (to leading order in g_s and alpha') on T^n fibrations over
S^1 with O(n,n;Z) monodromy. We also discuss the (approximate) moduli space of
such branes and argue that it is always geometric. For a D-brane located at a
point on the base N, the classical ``D-geometry'' is a T^n fibration over a
multiple cover of N.

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The categories of this paper are: cond-mat
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: physics