Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Birational geometry of del Pezzo fibrations with terminal quotient
  singularities   Del Pezzo fibrations appear as minimal models of rationally connected
varieties. The rationality of smooth del Pezzo fibrations is a well studied
question but smooth fibrations are not dense in moduli. Little is known about
the rationality of the singular models. We prove birational rigidity, hence
non-rationality, of del Pezzo fibrations with simple non-Gorenstein
singularities satisfying the famous $K^2$-condition. We then apply this result
to study embeddings of $\operatorname{PSL}_2(7)$ into the Cremona group.

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The categories of this paper are: math-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: q-fin
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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
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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: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: q-alg
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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: atom-ph