Percorrer por autor "Costa, J. C."
A mostrar 1 - 3 de 3
Resultados por página
Opções de ordenação
- On κ-reducibility of pseudovarieties of the form V ∗DPublication . Costa, J. C.; Teixeira, M. L.; Nogueira, ConceiçãoThis paper deals with the reducibility property of semidirect products of the form V∗D relatively to graph equation systems, where D denotes the pseudovariety of definite semigroups. We show that, if the pseudovariety V is reducible with respect to the canonical signature κ consisting of the multiplication and the (ω − 1)-power, then V ∗ D is also reducible with respect to κ.
- Semigroup presentations for test local groupsPublication . Costa, J. C.; Nogueira, C.; Teixeira, M. L.In this paper we exhibit a type of semigroup presentation which determines a class of local groups. We show that the finite elements of this class generate the pseudovariety LG of all finite local groups and use them as test-semigroups to prove that LG and S, the pseudovariety of all finite semigroups, verify the same $κ-identities involving κ-terms of rank at most 1, where κ denotes the implicit signature consisting of the multiplication and the (ω-1)-power.
- The word problem for κ-terms over the pseudovariety of local groupsPublication . Costa, J. C.; Nogueira, C.; Teixeira, M. L.In this paper we study the κ-word problem for the pseudovariety LG of local groups, where κ is the canonical signature consisting of the multiplication and the pseudoinversion. We solve this problem by transforming each arbitrary κ-term α into another one α∗ called the LG-canonical form of α and by showing that different canonical forms have different interpretations over LG. The procedure of construction of these canonical forms consists in applying reductions determined by a set Σ of κ-identities. As a consequence, Σ is a basis of κ-identities for the κ-variety generated by LG.