A common generalization of Kelley's theorem (concerning measures on Boolean algebra) and on von Neumann's minimax theorem
A comparison of some generalizations of Green's relations.
A completion theorem for finitely generated commutative semigroups.
A concept of variety for regular biordered sets.
A conjecture on the concatenation product
In a previous paper, the authors studied the polynomial closure of a variety of languages and gave an algebraic counterpart, in terms of Mal’cev products, of this operation. They also formulated a conjecture about the algebraic counterpart of the boolean closure of the polynomial closure – this operation corresponds to passing to the upper level in any concatenation hierarchy. Although this conjecture is probably true in some particular cases, we give a counterexample in the general case. Another...
A conjecture on the concatenation product
In a previous paper, the authors studied the polynomial closure of a variety of languages and gave an algebraic counterpart, in terms of Mal'cev products, of this operation. They also formulated a conjecture about the algebraic counterpart of the boolean closure of the polynomial closure – this operation corresponds to passing to the upper level in any concatenation hierarchy. Although this conjecture is probably true in some particular cases, we give a counterexample in the general case....
A construction of inverse semigroups.
A construction of right groups from a connected groupoid.
A counterexample in the cohomology of monoids.
A counter-example on *-embeddability into proper *-rings.
A counting theorem in the semigroup of circulant Boolean matrices
A cross section theorem for certain compact abelian semigroups.
A Family of Bisimple Inverse Semigroups.
A - finite actions and their automorphism groups.
A finiteness condition for finitely generated semigroups.
A finiteness condition for finitely generated semigroups.
A finiteness condition for semigroups which generalizes Green-Rees' theorem.
A fixed point characterization of cofinite languages.
A functional treatment of right invariant holoids.
A Game Theoretical Approach to The Algebraic Counterpart of The Wagner Hierarchy : Part II
The algebraic counterpart of the Wagner hierarchy consists of a well-founded and decidable classification of finite pointed ω-semigroups of width 2 and height ωω. This paper completes the description of this algebraic hierarchy. We first give a purely algebraic decidability procedure of this partial ordering by introducing a graph representation of finite pointed ω-semigroups allowing to compute their precise Wagner degrees. The Wagner degree of any ω-rational language can therefore be computed...