Regular pairings of functors and weak (co)monads

For functors \(L:\mathbb{A}\to \mathbb{B}\) and \(R:\mathbb{B}\to \mathbb{A}\) betweenany categories \(\mathbb{A}\) and \(\mathbb{B}\), a  pairing is defined by maps, natural in \(A\in \mathbb{A}\) and  \(B\in \mathbb{B}\),\[\xymatrix{{\rm Mor}_\mathbb{B} (L(A),B) \ar@<0.5ex>[r]^{\alph...

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Дата:2018
Автор: Wisbauer, Robert
Формат: Стаття
Мова:English
Опубліковано: Lugansk National Taras Shevchenko University 2018
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Онлайн доступ:https://admjournal.luguniv.edu.ua/index.php/adm/article/view/738
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Назва журналу:Algebra and Discrete Mathematics

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Algebra and Discrete Mathematics
id oai:ojs.admjournal.luguniv.edu.ua:article-738
record_format ojs
spelling oai:ojs.admjournal.luguniv.edu.ua:article-7382018-04-26T00:47:27Z Regular pairings of functors and weak (co)monads Wisbauer, Robert pairing of functors; adjoint functors; weak monads and comonads; \(r\)-unital monads; \(r\)-counital comonads 18A40, 18C20, 16T15 For functors \(L:\mathbb{A}\to \mathbb{B}\) and \(R:\mathbb{B}\to \mathbb{A}\) betweenany categories \(\mathbb{A}\) and \(\mathbb{B}\), a  pairing is defined by maps, natural in \(A\in \mathbb{A}\) and  \(B\in \mathbb{B}\),\[\xymatrix{{\rm Mor}_\mathbb{B} (L(A),B) \ar@<0.5ex>[r]^{\alpha} & {\rm Mor}_\mathbb{A} (A,R(B))\ar@<0.5ex>[l]^{\beta}}.\] \((L,R)\) is an adjoint pair provided \(\alpha\) (or \(\beta\)) is a bijection. In this case the composition \(RL\) defines a monad on the category \(\mathbb{A}\),  \(LR\) defines a comonad on the category \(\mathbb{B}\), and there is a well-known correspondence between monads (or comonads) and adjoint pairs of functors.For various applications it was observed that the conditions for a unit of a monad was too restrictive and weakening it still allowed for a useful generalised notion of a monad. This led to the introduction of weak monads and weak comonads and the definitions needed were made without referring to this kind of adjunction. The motivation for the present paper is to show that these notions can be naturally derived from pairings of functors  \((L,R,\alpha,\beta)\) with  \(\alpha = \alpha\cdot \beta\cdot \alpha\) and \(\beta = \beta \cdot\alpha\cdot\beta\).  Following closely the constructions known for monads (and unital modules) and comonads (and counital comodules), we show that any weak (co)monad on \(\mathbb{A}\) gives rise to a regular pairing between \(\mathbb{A}\) and the category of compatible (co)modules. Lugansk National Taras Shevchenko University 2018-04-26 Article Article Peer-reviewed Article application/pdf https://admjournal.luguniv.edu.ua/index.php/adm/article/view/738 Algebra and Discrete Mathematics; Vol 15, No 1 (2013) 2415-721X 1726-3255 en https://admjournal.luguniv.edu.ua/index.php/adm/article/view/738/269 Copyright (c) 2018 Algebra and Discrete Mathematics
institution Algebra and Discrete Mathematics
collection OJS
language English
topic pairing of functors; adjoint functors; weak monads and comonads; \(r\)-unital monads; \(r\)-counital comonads
18A40
18C20
16T15
spellingShingle pairing of functors; adjoint functors; weak monads and comonads; \(r\)-unital monads; \(r\)-counital comonads
18A40
18C20
16T15
Wisbauer, Robert
Regular pairings of functors and weak (co)monads
topic_facet pairing of functors; adjoint functors; weak monads and comonads; \(r\)-unital monads; \(r\)-counital comonads
18A40
18C20
16T15
format Article
author Wisbauer, Robert
author_facet Wisbauer, Robert
author_sort Wisbauer, Robert
title Regular pairings of functors and weak (co)monads
title_short Regular pairings of functors and weak (co)monads
title_full Regular pairings of functors and weak (co)monads
title_fullStr Regular pairings of functors and weak (co)monads
title_full_unstemmed Regular pairings of functors and weak (co)monads
title_sort regular pairings of functors and weak (co)monads
description For functors \(L:\mathbb{A}\to \mathbb{B}\) and \(R:\mathbb{B}\to \mathbb{A}\) betweenany categories \(\mathbb{A}\) and \(\mathbb{B}\), a  pairing is defined by maps, natural in \(A\in \mathbb{A}\) and  \(B\in \mathbb{B}\),\[\xymatrix{{\rm Mor}_\mathbb{B} (L(A),B) \ar@<0.5ex>[r]^{\alpha} & {\rm Mor}_\mathbb{A} (A,R(B))\ar@<0.5ex>[l]^{\beta}}.\] \((L,R)\) is an adjoint pair provided \(\alpha\) (or \(\beta\)) is a bijection. In this case the composition \(RL\) defines a monad on the category \(\mathbb{A}\),  \(LR\) defines a comonad on the category \(\mathbb{B}\), and there is a well-known correspondence between monads (or comonads) and adjoint pairs of functors.For various applications it was observed that the conditions for a unit of a monad was too restrictive and weakening it still allowed for a useful generalised notion of a monad. This led to the introduction of weak monads and weak comonads and the definitions needed were made without referring to this kind of adjunction. The motivation for the present paper is to show that these notions can be naturally derived from pairings of functors  \((L,R,\alpha,\beta)\) with  \(\alpha = \alpha\cdot \beta\cdot \alpha\) and \(\beta = \beta \cdot\alpha\cdot\beta\).  Following closely the constructions known for monads (and unital modules) and comonads (and counital comodules), we show that any weak (co)monad on \(\mathbb{A}\) gives rise to a regular pairing between \(\mathbb{A}\) and the category of compatible (co)modules.
publisher Lugansk National Taras Shevchenko University
publishDate 2018
url https://admjournal.luguniv.edu.ua/index.php/adm/article/view/738
work_keys_str_mv AT wisbauerrobert regularpairingsoffunctorsandweakcomonads
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