Very-Well-Behaved Epireflections for Categories of Models of Sketches

Fuente: arXiv
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Autore principale: Xarez, João J.
Natura: Preprint
Pubblicazione: 2025
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author Xarez, João J.
author_facet Xarez, João J.
contents Firstly, precise conditions on how to obtain very-well-behaved epireflections are explored and improved from the author's previous papers; meaning that, beginning with a monad and a prefactorization system on a category, is produced a reflection with stable units (stronger than semi-left-exactness, also called admissibility in categorical Galois Theory) and an associated monotone-light factorization. Then, we were able to show that, for a pseudo-filtered category J in which every arrow is a monomorphism, the colimit functor on Set^J produces a very-well-behaved epireflection; if J = 2 the monotone-light factorization is non-trivial, as showed as an example. Then, new results are presented that grant very-well-behaved subreflections from the very-well-behaved reflections induced by an adjunction given by right Kan extensions for presheaves. These subreflections are obtained by restricting to the models of a sketch; it is showed finally that the known very-well-behaved reflection of n-categories into n-preorders is an example of this process (being n any positive integer).
format Preprint
id arxiv_https___arxiv_org_abs_2509_07241
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Very-Well-Behaved Epireflections for Categories of Models of Sketches
Xarez, João J.
Category Theory
18A40, 18A32, 18E50, 18N50, 18F20, 18C30, 18N10
Firstly, precise conditions on how to obtain very-well-behaved epireflections are explored and improved from the author's previous papers; meaning that, beginning with a monad and a prefactorization system on a category, is produced a reflection with stable units (stronger than semi-left-exactness, also called admissibility in categorical Galois Theory) and an associated monotone-light factorization. Then, we were able to show that, for a pseudo-filtered category J in which every arrow is a monomorphism, the colimit functor on Set^J produces a very-well-behaved epireflection; if J = 2 the monotone-light factorization is non-trivial, as showed as an example. Then, new results are presented that grant very-well-behaved subreflections from the very-well-behaved reflections induced by an adjunction given by right Kan extensions for presheaves. These subreflections are obtained by restricting to the models of a sketch; it is showed finally that the known very-well-behaved reflection of n-categories into n-preorders is an example of this process (being n any positive integer).
title Very-Well-Behaved Epireflections for Categories of Models of Sketches
topic Category Theory
18A40, 18A32, 18E50, 18N50, 18F20, 18C30, 18N10
url https://arxiv.org/abs/2509.07241