306 citations
Counting papers with at most 25 authors, so collaboration author lists do not stand in for the people here.
- Universidade do PortoPT174 papers
- University of CoimbraPT98 papers
- University of MinhoPT81 papers
- University of LisbonPT24 papers
- Centre National de la Recherche ScientifiqueFR22 papers
- Instituto Superior TécnicoPT22 papers
- UCLouvainBE13 papers
- Universidade Federal da BahiaBR13 papers
- Centro de Análise Matemática Geometria e Sistemas DinâmicosPT10 papers
- Pontifícia Universidade Católica do Rio de JaneiroBR10 papers
- Universidad de La LagunaES9 papers
- Universidade Federal do Rio de JaneiroBR9 papers
20 papers · 1 filter
Facets of congruence distributivity in Goursat categories
Marino Gran, Diana Rodelo, Idriss Tchoffo Nguefeu
We give new characterisations of regular Mal'tsev categories with distributive lattice of equivalence relations through variations of the so-called Triangular Lemma and Trapezoid L…
Semantic Factorization and Descent
Fernando Lucatelli Nunes
Let be a -category with suitable opcomma objects and pushouts. We give a direct proof that, provided that the codensity monad of a morphism exists and is preser…
Cancellative conjugation semigroups and monoids
A. P. Garrão, N. Martins-Ferreira, M. Raposo +1
We show that the category of cancellative conjugation semigroups is weakly Mal'tsev and give a characterization of all admissible diagrams there. In the category of cancellative co…
Pseudoalgebras and non-canonical isomorphisms
Fernando Lucatelli Nunes
Given a pseudomonad , we prove that a lax -morphism between pseudoalgebras is a -pseudomorphism if and only if there is a suitable (possib…
Some remarks on protolocalizations and protoadditive reflections
Maria Manuel Clementino, Marino Gran, George Janelidze
We investigate additional properties of protolocalizations, introduced and studied by F. Borceux, M. M. Clementino, M. Gran, and L. Sousa, and of protoadditive reflections, introdu…
Aspects of algebraic Algebras
Dirk Hofmann, Lurdes Sousa
In this paper we investigate important categories lying strictly between the Kleisli category and the Eilenberg-Moore category, for a Kock-Zöberlein monad on an order-enriched cate…
On some categorical-algebraic conditions in S-protomodular categories
Nelson Martins-Ferreira, Andrea Montoli, Manuela Sobral
In the context of protomodular categories, several additional conditions have been considered in order to obtain a closer group-like behavior. Among them are locally algebraic cart…
Two characterisations of groups amongst monoids
Andrea Montoli, Diana Rodelo, Tim Van der Linden
The aim of this paper is to solve a problem proposed by Dominique Bourn: to provide a categorical-algebraic characterisation of groups amongst monoids and of rings amongst semiring…
What is an ideal a zero-class of?
N. Martins-Ferreira, A. Montoli, A. Ursini +1
We characterise, in pointed regular categories, the ideals as the zero-classes of surjective relations. Moreover, we study a variation of the "Smith is Huq" condition: two surjecti…
Lax orthogonal factorisation systems
Maria Manuel Clementino, Ignacio Lopez Franco
This paper introduces lax orthogonal algebraic weak factorisation systems on 2-categories and describes a method of constructing them. This method rests in the notion of simple 2-m…
Higher central extensions and cohomology
Diana Rodelo, Tim Van der Linden
We establish a Galois-theoretic interpretation of cohomology in semi-abelian categories: cohomology with trivial coefficients classifies central extensions, also in arbitrarily hig…
Further remarks on the "Smith is Huq" condition
Nelson Martins-Ferreira, Tim Van der Linden
We compare the 'Smith is Huq' condition (SH) with three commutator conditions in semi-abelian categories: first an apparently weaker condition which arose in joint work with Bourn…
Approximate Hagemann-Mitschke co-operations
Diana Rodelo, Tim Van der Linden
We show that varietal techniques based on the existence of operations of a certain arity can be extended to n-permutable categories with binary coproducts. This is achieved via wha…
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…
Pointed homotopy and pointed lax homotopy of 2-crossed module maps
Bjorn Gohla, Joao Faria Martins
We address the (pointed) homotopy theory of 2-crossed modules (of groups), which are known to faithfully represent Gray 3-groupoids, with a single object, and also connected homoto…
Relative Commutator Theory in Semi-Abelian Categories
Tomas Everaert, Tim Van der Linden
Basing ourselves on the concept of double central extension from categorical Galois theory, we study a notion of commutator which is defined relative to a Birkhoff subcategory B of…
The ternary commutator obstruction for internal crossed modules
Manfred Hartl, Tim Van der Linden
In finitely cocomplete homological categories, co-smash products give rise to (possibly higher-order) commutators of subobjects. We use binary and ternary co-smash products and the…
A note on the "Smith is Huq" condition
Nelson Martins-Ferreira, Tim Van der Linden
We show that two known conditions which arose naturally in commutator theory and in the theory of internal crossed modules coincide: every star-multiplicative graph is multiplicati…
Perfect category-graded algebras
Ana Paula Santana, Ivan Yudin
In a perfect category every object has a minimal projective resolution. We give a criterion for the category of modules over a categorygraded algebra to be perfect.