On the notion of precohomology
On the preservation of homotopy invariance by Kan extensions
On the pullback stability of a quotient map with respect to a closure operator.
On the reflective hull problem
On the size of categories.
On the Whitehead theorem in shape theory II
On Underlying Functors in General and Topological Algebra.
On weak monomorphisms and weak epimorphisms in the category of pro-groups.
In this paper we characterize weak monomorphisms and weak epimorphisms in the category of pro-groups. Also we define the notion of weakly exact sequence and we study this notion in the category of pro-groups.
One example concerning testing categories
One folkloristic lemma on cardinal reflections in Unif
One more remark on reflections
One obstruction for closedness
Operads in higher-dimensional category theory.
Opérations sur les cartes et métamorphoses de la catégorie des G-ensembles.
We call metamorphosis of a given category an autoequivalence functor up to within natural equivalence. We show that, given a group G, the group of metamorphoses of the category of G-sets (as well as the corresponding group for ?sufficiently big? subcategories) may be naturally identified to the group of outer automorphism of G. We get by this way a natural description of a group of known operations on tessellations of a surface: the identity operation, the Poincaré duality, and four others which...
Order-enriched solid functors
Order-enriched solid functors, as presented in this paper in two versions, enjoy many of the strong properties of their ordinary counterparts, including the transfer of the existence of weighted (co)limits from their codomains to their domains. The ordinary version of the notion first appeared in Trnková's work on automata theory of the 1970s and was subsequently studied by others under various names, before being put into a general enriched context by C. Anghel. Our focus in this paper is on differentiating...
Ordinal invariants and epimorphisms in some categories of weak Hausdorff spaces
Orthogonal and prereflective subcategories
Orthogonality and closure operators