Abstract
The category R e l is the category of sets (objects) and relations (morphisms). Equipped with the direct product of sets, R e l is a monoidal category. Moreover, R e l is a locally posetal 2-category, since every homset R e l(A,B) is a poset with respect to inclusion. We examine the 2-category of monoids R e l M o n in this category. The morphism we use are lax. This category includes, as subcategories, various interesting classes: hypergroups, partial monoids (which include various types of quantum logics, for example effect algebras) and small categories. We show how the 2-categorical structure gives rise to several previously defined notions in these categories, for example certain types of congruence relations on generalized effect algebras. This explains where these definitions come from.
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We are indebted to both anonymous referees for valuable comments and suggestions.
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This research is supported by grants VEGA 2/0069/16, 1/0420/15, Slovakia and by the Slovak Research and Development Agency under the contract APVV-14-0013.
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Jenčová, A., Jenča, G. On Monoids in the Category of Sets and Relations. Int J Theor Phys 56, 3757–3769 (2017). https://doi.org/10.1007/s10773-017-3304-z
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DOI: https://doi.org/10.1007/s10773-017-3304-z