Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comodules, contramodules and Pontryagin duality   Let $C$ be a $k$-coalgebra, where $k$ is a field. The category of
pseudocompact left $C^*$-modules is dual to both the category of discrete right
$C^*$-modules and to the category of left $C$-comodules. We obtain this way two
sides of a square of dualities. In this note we complete the square by
introducing as fourth corner the category of pseudocompact right
$C$-contramodules. We use these dualities to extend a natural isomorphism of
Takeuchi.

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The categories of this paper are: q-alg
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The categories of this paper are: eess
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
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The categories of this paper are: comp-gas
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The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: econ
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The categories of this paper are: bayes-an