Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: K3 surfaces without section as double covers of Halphen surfaces, and
  F-theory compactifications   We construct several examples of genus-one fibered K3 surfaces without a
global section with type $I_{n}$ fibers, by considering double covers of a
special class of rational elliptic surfaces lacking a global section, known as
Halphen surfaces of index 2. The resulting K3 surfaces have bisection
geometries. F-theory compactifications on these K3 genus-one fibrations without
a section times a K3 yield models that have $SU(n)$ gauge symmetries with a
discrete $\mathbb{Z}_2$ symmetry.

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The categories of this paper are: astro-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: solv-int