We completely determine all commutative semigroup varieties that are cancellable elements of the lattice SEM of all semigroup varieties. In particular, we verify that a commutative semigroup variety is a cancellable element ...

A convolution is a mapping C of the set Z + of positive integers into the set P(Z +) of all subsets of Z + such that,for any n ∈ Z +, each member of C(n) is a divisor of n. If D(n) is the set of all divisors of n, for any ...

Nowadays, we witness changing trends in terms of the interest in language learning. In Poland, more and more higher education establishments, not only public, but also private, introduce various types of majors concerning ...

In this paper we prove that the group (Zp) 2 × Zq ×Zr is CI-group, where p, q, r are primes such that q and r divide p − 1, and r divides q − 1.

In this paper the well-known connection between hyperidentities of an algebra and identities satisfied by the clone of this algebra is studied in a restricted setting, that of n-ary full hyperidentities and identities of ...

We accomplish the classification of Cohen–Macaulay modules over the curve singularities of type T44 and the description of the corresponding matrix factorizations, started in.

Let X be a set of cardinality k, F be a family of subsets of X. We say that a cardinal , < k, is a color-detector of the hypergraph H = (X,F) if card (X) for every coloring : X ! k such that card (F) for ...

We introduce the notion of connection thickness of spheres in a Cayley graph, related to dead-ends and their retreat depth. It was well-known that connection thickness is bounded for finitely presented one-ended groups. ...

The problems of the development of the corporate culture of enterprises are becoming more and more relevant in modern business conditions. In this regard, the terminological apparatus regarding the essence and content of ...