Paramedial groupoids
Perfectness of certain subsemigroups of a perfect semigroup.
Permutation group extension of groupoids.
Presentations for subsemigroups of
Let be an -chain. We give presentations for the following transformation semigroups: the semigroup of full order-decreasing mappings of , the semigroup of partial one-to-one order-decreasing mappings of , the semigroup of full order-preserving and order-decreasing mappings of , the semigroup of partial one-to-one order-preserving and order-decreasing mappings of , and the semigroup of partial order-preserving and order-decreasing mappings of .
Principal ideals of finitely generated commutative monoids
We study the semigroups isomorphic to principal ideals of finitely generated commutative monoids. We define the concept of finite presentation for this kind of semigroups. Furthermore, we show how to obtain information on these semigroups from their presentations.
Productive representations of semigroups by pairs of structures
Products of metric, uniform and topological spaces
Products of topological spaces represent any semigroup (Preliminary communication)