AUTOMATE is a package for symbolic computation on nite automata, extended rational expressions and nite semigroups. On the one hand, it enables one to compute the deterministic minimal automaton of the language represented by a rational expression or given by its table. On the other hand, given the transition table of a deterministic automaton, AUTOMATE computes the associated transition monoid...

We extend the notion of a purely infinite simple C*-algebra to the context of unital rings, and we study its basic properties, specially those related to K-Theory. For instance, if R is a purely infinite simple ring, then K0(R) + = K0(R), the monoid of isomorphism classes of finitely generated projective R-modules is isomorphic to the monoid obtained from K0(R) by adjoining a new zero element, ...

Let M be an irreducible normal algebraic monoid with unit group G. It is known that G admits a Rosenlicht decomposition, G = GantGaff ∼= (Gant ×Gaff )/Gaff ∩Gant, where Gant is the maximal anti-affine subgroup of G, and Gaff the maximal normal connected affine subgroup of G. In this paper we show that this decomposition extends to a decomposition M = GantMaff ∼= Gant∗Gaff∩GantMaff , whereMaff i...

The main goal of this work is the investigation of some properties of co-regular languages. In many applications it is important to handle innnite sets of terms. We represent two equivalent formalisms for nite deened innnite sets of term substitutions which are leading to co-regular languages. As it will be proved later the co-regular languages are monoidic homomorphical images of regular langu...

A factorizable inverse monoid can be identified, up to isomorphism, with an inverse submonoid M of a symmetric inverse monoid I(X) where each element of M is a restriction of a permutation of X belonging to M . So factorizable inverse monoids are natural objects, and appear in a number of branches of mathematics, cf. [12], [4]. The notion of an almost factorizable inverse semigroup was introduc...

the aim of this paper is to study semigroups possessing $e$-regular elements, where an element $a$ of a semigroup $s$ is {em $e$-regular} if $a$ has an inverse $a^circ$ such that $aa^circ,a^circ a$ lie in $ esubseteq e(s)$. where $s$ possesses `enough' (in a precisely defined way) $e$-regular elements, analogues of green's lemmas and even of green's theorem hold, where green&apos...

The domatic number of a graph G, denoted dom(G), is the maximum possible cardinality of a family of disjoint sets of vertices of G, each set being a dominating set of G. It is well known that every graph without isolated vertices has dom(G) ≥ 2. For every k, it is known that there are graphs with minimum degree at least k and with dom(G) = 2. In this paper we prove that this is not the case if ...

For a tournament T , let ν3(T ) denote the maximum number of pairwise edge-disjoint triangles (directed cycles of length 3) in T . Let ν3(n) denote the minimum of ν3(T ) ranging over all regular tournaments with n vertices (n odd). We conjecture that ν3(n) = (1 + o(1))n /9 and prove that n 11.43 (1− o(1)) ≤ ν3(n) ≤ n 9 (1 + o(1)) improving upon the best known upper bound of n −1 8 and lower bou...