Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Orientifolds, hypercharge embeddings and the Standard Model   The embedding of the SM hypercharge into an orientifold gauge group is
studied. Possible embeddings are classified, and a systematic construction of
bottom-up configurations and top-down orientifold vacua is achieved, solving
the tadpole conditions in the context of Gepner orientifolds. Some hypercharge
embeddings are strongly preferred compared to others. Configurations with
chiral antisymmetric tensors are suppressed. We find among others, genuine
examples of supersymmetric SU(5), flipped SU(5), Pati-Salam and trinification
vacua with no chiral exotics.

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The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg