Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-BPS States and Branes in String Theory   We review the recent developments in our understanding of non-BPS states and
branes in string theory. The topics include 1) construction of unstable non-BPS
D-branes in type IIA and type IIB string theories, 2) construction of stable
non-BPS D-branes on various orbifolds and orientifolds of type II string
theories, 3) description of BPS and non-BPS D-branes as tachyonic soliton
solutions on brane-antibrane pair of higher dimension, and 4) study of the
spectrum of non-BPS states and branes on a system of coincident D-brane -
orientifold plane system. Some other related results are also discussed
briefly.

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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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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: physics
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph