44 citations · 366 across the 37 of their papers we have counts for
5 papers · 1 filter
On the normality of Higgins commutators
Alan S. Cigoli, James R. A. Gray, Tim Van der Linden
In a semi-abelian context, we study the condition (NH) asking that Higgins commutators of normal subobjects are normal subobjects. We provide examples of categories that do or do n…
The fundamental group functor as a Kan extension
Tomas Everaert, Julia Goedecke, Tim Van der Linden
We prove that the fundamental group functor from categorical Galois theory may be computed as a Kan extension.
An observation on n-permutability
Nelson Martins-Ferreira, Diana Rodelo, Tim Van der Linden
We prove that in a regular category all reflexive and transitive relations are symmetric if and only if every internal category is an internal groupoid. In particular, these condit…
A decomposition formula for the weighted commutator
Nelson Martins-Ferreira, Tim Van der Linden
We decompose the weighted subobject commutator of M. Gran, G. Janelidze and A. Ursini as a join of a binary and a ternary commutator.
Universal central extensions in semi-abelian categories
Jose Manuel Casas, Tim Van der Linden
Basing ourselves on Janelidze and Kelly's general notion of central extension, we study universal central extensions in the context of semi-abelian categories. We consider a new fu…