Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An extension of Kracht's theorem to generalized Sahlqvist formulas   Sahlqvist formulas are a syntactically specified class of modal formulas
proposed by Hendrik Sahlqvist in 1975. They are important because of their
first-order definability and canonicity, and hence axiomatize complete modal
logics. The first-order properties definable by Sahlqvist formulas were
syntactically characterized by Marcus Kracht in 1993. The present paper extends
Kracht's theorem to the class of `generalized Sahlqvist formulas' introduced by
Goranko and Vakarelov and describes an appropriate generalization of Kracht
formulas.

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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: econ