On nets of free polygons over a category and their categories of homomorphisms
On Nilpotent Subsemigroups in some Matrix Semigroups
2000 Mathematics Subject Classification: 20M20, 20M10.We describe maximal nilpotent subsemigroups of a given nilpotency class in the semigroup Ωn of all n × n real matrices with non-negative coefficients and the semigroup Dn of all doubly stochastic real matrices.
On normal semigroups
On numerical semigroups.
On one definition of grammatical categories
On optimal factorization of free semigroups into free subsemigroups.
On ordered left groups.
On ordered regular semigroups with biggest inverses.
On p -semisimple S-sets.
On partial cohomologies of semigroups.
On Periodic Semigroups with One-Sided Identities
On permutability in semigroup varieties
The paper contains characterizations of semigroup varieties whose semigroups with one generator (two generators) are permutable. Here all varieties of regular -semigroups are described in which each semigroup with two generators is permutable.
On permutation properties in groups and semigroups.
On P-injective hulls of S-sets.
On p-irreducible S-subsets of an S-set.
On power commutative semigroups.
On presentations of Brauer-type monoids
We obtain presentations for the Brauer monoid, the partial analogue of the Brauer monoid, and for the greatest factorizable inverse submonoid of the dual symmetric inverse monoid. In all three cases we apply the same approach, based on the realization of all these monoids as Brauer-type monoids.
On presentations of semigroup rings
Siano un ideale di un anello e una congruenza su un semigruppo . Consideriamo l'anello semigruppo come un'immagine omomorfa dell'anello semigruppo . Questo è fatto in tre passi: prima studiando l'anello semigruppo , poi e infine combinando i due casi speciali. In ciascun caso, determiniamo l'ideale che è il nucleo dell'omomorfismo in questione. I risultati corrispondenti per le -algebre, dove è un anello commutativo, possono essere facilmente dedotti. Alcuni raffinamenti, casi speciali...
On primary semigroups
On prime fuzzy bi-ideals in ternary semigroups