Given a semilattice X we study the algebraic properties of the semigroup υ(X) of upfamilies on X. The semigroup υ(X) contains the Stone-ˇCech extension β(X), the superextension λ(X), and the space of filters φ(X) on X as ...

A Cayley graph X = Cay(G, S) is called normal for G if the right regular representation R(G) of G is normal in the full automorphism group Aut(X) of X. In the present paper it is proved that all connected tetravalent Cayley ...

In this paper the metacyclic Miller-Moreno p-groups which appear as the additive groups of finite local nearrings are classified.

Let G be a finite group. A subgroup A is called:1) S-quasinormal in G if A is permutable with all Sylow subgroups in G 2) S-quasinormally embedded in G if every Sylow subgroup of A is a Sylow subgroup of some S-quasinormal ...

A subset A of a group G is called sparse if, for every infinite subset X of G, there exists a finite subset F ⊂ X, such that ∩x∈FxA is finite. We denote by η(G) the minimal cardinal such that G can be partitioned in η(G) ...

For two vertices u and v in a graph G = (V, E), the detour distance D(u, v) is the length of a longest u-v path in G. A u-v path of length D(u, v) is called a u-v detour. For subsets A and B of V, the detour distance D(A, ...