Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Undecidable iterative propositional calculus   In this paper, we consider iterative propositional calculi, which are finite
sets of propositional formulas together with the rules of modus ponens and weak
substitution (when formula being substituted must be already inferred). We
construct an undecidable iterative propositional calculus using axioms in 3
variables. Particulary, we show that the general problem of derivability for
these calculi is undecidable.

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The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: econ
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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: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph