1 citations · 6 across the 15 of their papers we have counts for
19 papers
What is an internal groupoid?
Nelson Martins-Ferreira
An answer to the question investigated in this paper brings a new characterization of internal groupoids such that: (a) it holds even when finite limits are not assumed to exist; (…
On the normality of monoid monomorphisms
Nelson Martins-Ferreira, Manuela Sobral
In the category of monoids we characterize monomorphisms that are normal, in an appropriate sense, to internal reflexive relations, preorders or equivalence relations. The zero-cla…
Pointed semibiproducts of monoids
Nelson Martins-Ferreira
Semibiproducts of monoids are introduced here as a common generalization to biproducts (of abelian groups) and to semidirect products (of groups) for exploring a wide class of mono…
A refinement of ternary Boolean algebras
J. P. Fatelo, N. Martins-Ferreira
An algebraic structure with two constants and one ternary operation, which is not completely commutative, is put forward to accommodate ternary Boolean algebras. When the ternary o…
Semi-biproducts of monoids
Nelson Martins-Ferreira
It is shown that the category of \emph{semi-biproducts} of monoids is equivalent to the category of \emph{pseudo-actions}. A semi-biproduct of monoids is a new notion, obtained thr…
Affine mobi spaces
J. P. Fatelo, N. Martins-Ferreira
The category of mobi algebras has been introduced as a model to the unit interval of real numbers. The notion of mobi space over a mobi algebra has been proposed as a model for spa…