A doppelsemigroup is an algebraic system consisting of a set with two binary associative operations satisfying certain identities. Doppelsemigroups are a generalization of semi-groups and they have relationships with such ...

Let Cay(S, A) denote the Cayley digraph of the semigroup S with respect to the set A, where A is any subset of S. The function f : Cay(S, A) → Cay(S, A) is called an endo-morphism of Cay(S, A) if for each (x, y) ∈ E(Cay(S, ...

Abstract . A graph G is called a graphoidal graph if there exists a graph H and a graphoidal cover ψ of H such that G ∼= Ω(H, ψ). Then the graph G is said to be self-graphoidal if it is isomorphic to one of its graphoidal ...

We study asymptotics of the spectral measure of a randomly chosen partial automorphism of a rooted tree. To every partial automorphism x we assign its action matrix Ax. It is shown that the uniform distribution on eigenvalues ...