Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Penrose Limits of Orbifolds and Orientifolds   We study the Penrose limit of various AdS_p X S^q orbifolds. The limiting
spaces are waves with parallel rays and singular wave fronts. In particular, we
consider the orbifolds AdS_3 X S^3/\Gamma, AdS_5 X S^5/\Gamma and AdS_{4,7} X
S^{7,4}/\Gamma where \Gamma acts on the sphere and/or the AdS factor. In the
pp-wave limit, the wave fronts are the orbifolds C^2/\Gamma, C^4/\Gamma and R
XC^4/\Gamma, respectively. When desingularization is possible, we get
asymptotically locally pp-wave backgrounds (ALpp). The Penrose limit of
orientifolds are also discussed. In the AdS_5 X RP^5 case, the limiting
singularity can be resolved by an Eguchi-Hanson gravitational instanton. The
pp-wave limit of D3-branes near singularities in F-theory is also presented.
Finally, we give the embedding of D-dimensional pp-waves in flat M^{2,D} space.

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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys