Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discrete Torsion   In this article we explain discrete torsion. Put simply, discrete torsion is
the choice of orbifold group action on the B field. We derive the
classification H^2(G, U(1)), we derive the twisted sector phases appearing in
string loop partition functions, we derive M. Douglas's description of discrete
torsion for D-branes in terms of a projective representation of the orbifold
group, and we outline how the results of Vafa-Witten fit into this framework.
In addition, we observe that additional degrees of freedom (known as shift
orbifolds) appear in describing orbifold group actions on B fields, in addition
to those classified by H^2(G, U(1)), and explain how these new degrees of
freedom appear in terms of twisted sector contributions to partition functions
and in terms of orbifold group actions on D-brane worldvolumes. This paper
represents a technically simplified version of prior papers by the author on
discrete torsion. We repeat here technically simplified versions of results
from those papers, and have included some new material.

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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
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The categories of this paper are: cs