12 citations · 23 across the 10 of their papers we have counts for
7 papers · 1 filter
Recognizing pro-R closures of regular languages
Jorge Almeida, José Carlos Costa, Marc Zeitoun
Given a regular language L, we effectively construct a unary semigroup that recognizes the topological closure of L in the free unary semigroup relative to the variety of unary sem…
On -reducibility of pseudovarieties of the form
José Carlos Costa, Conceição Nogueira, M. Lurdes Teixeira
This paper deals with the reducibility property of semidirect products of the form relatively to graph equation systems, where denotes the pseudovariety of de…
The word problem for -terms over the pseudovariety of local groups
J. C. Costa, C. Nogueira, M. L. Teixeira
In this paper we study the -word problem for the pseudovariety of local groups, where is the canonical signature consisting of the multiplication and the pseudoin…
Pointlike reducibility of pseudovarieties of the form
J. C. Costa, C. Nogueira, M. L. Teixeira
In this paper, we investigate the reducibility property of semidirect products of the form relatively to (pointlike) systems of equations of the form …
Reducibility of pointlike problems
J. Almeida, J. C. Costa, M. Zeitoun
We show that the pointlike and the idempotent pointlike problems are reducible with respect to natural signatures in the following cases: the pseudovariety of all finite semigroups…
Factoriality and the Pin-Reutenauer procedure
J. Almeida, J. C. Costa, M. Zeitoun
We consider implicit signatures over finite semigroups determined by sets of pseudonatural numbers. We prove that, under relatively simple hypotheses on a pseudovariety V of semigr…
Semigroup presentations for test local groups
J. C. Costa, C. Nogueira, M. L. Teixeira
In this paper we exhibit a type of semigroup presentations which determines a class of local groups. We show that the finite elements of this class generate the pseudovariety ${\bf…