Combinatorial properties of products of graphs
Combinatorial results for semigroups of order-decreasing partial transformations.
Combinatoric of syzygies for semigroup algebras.
We describe how the graded minimal resolution of certain semigroup algebras is related to the combinatorics of some simplicial complexes. We obtain characterizations of the Cohen-Macaulay and Gorenstein conditions. The Cohen-Macaulay type is computed from combinatorics. As an application, we compute explicitly the graded minimal resolution of monomial both affine and simplicial projective surfaces.
Comments on the permutation property for semigroups.
Commutation of operations and its relationship with Menger and Mann superpositions
The article considers a problem from Trokhimenko paper [13] concerning the study of abstract properties of commutations of operations and their connection with the Menger and Mann superpositions. Namely, abstract characterizations of some classes of operation algebras, whose signature consists of arbitrary families of commutations of operations, Menger and Mann superpositions and their various connections are found. Some unsolved problems are given at the end of the article.
Commutative archimedean cancellative semigroups without idempotent
Commutative cancellative semigroups with two generators
Commutative images of rational languages and the abelian kernel of a monoid
Natural algorithms to compute rational expressions for recognizable languages, even those which work well in practice, may produce very long expressions. So, aiming towards the computation of the commutative image of a recognizable language, one should avoid passing through an expression produced this way. We modify here one of those algorithms in order to compute directly a semilinear expression for the commutative image of a recognizable language. We also give a second modification of the algorithm...
Commutative images of rational languages and the Abelian kernel of a monoid
Natural algorithms to compute rational expressions for recognizable languages, even those which work well in practice, may produce very long expressions. So, aiming towards the computation of the commutative image of a recognizable language, one should avoid passing through an expression produced this way. We modify here one of those algorithms in order to compute directly a semilinear expression for the commutative image of a recognizable language. We also give a second modification of the algorithm...
Commutative monoids all of whose principal ideals are projective.
Commutative monoids with zero-divisors
We describe algorithms for computing the nilradical and the zero-divisors of a finitely generated commutative -monoid. These algorithms will be used for deciding if a given ideal of a finitely generated commutative -monoid is prime, radical or primary.
Commutative primary semigroups
Commutative semigroup cohomology.
Commutative semigroup rings which are principal ideal rings
Commutative semigroups having greatest regular images.
Commutative semigroups that are nil of index 2 and have no irreducible elements
Every commutative nil-semigroup of index 2 can be imbedded into such a semigroup without irreducible elements.
Commutative semigroups that are simple over thein endomorphism semirings
Commutative semigroups which are embeddable into epigroups.
Commutative semigroups whose homomorphic images in groups are groups.
Commutative semigroups whose lattice of tolerances is Boolean