Using (introduced by the first author) the method of (min, max)-equivalence, we classify all serial principal posets, i.e. the posets S satisfying the following conditions: (1) the quadratic Tits form qS(z) : Z |S|+1 ...

For a commutative ring R and an ideal I of R, the ideal-based zero-divisor graph is the undirected graph ΓI (R) with vertices {x ∈ R−I : xy ∈ I for some y ∈ R−I}, where distinct vertices x and y are adjacent if and only ...

In 1995 D. V. Belkin described the lattice of quasivarieties of modules over principal ideal domains [1]. The following paper provides a description of the lattice of subquasivarieties of the variety of modules over a given ...

Let D = (V, A) be a finite simple directed graph (shortly digraph). A function f : V −→ {−1, 1} is called a twin signed dominating function (TSDF) if f(N −[v]) > 1 and f(N +[v]) > 1 for each vertex v ∈ V . The twin signed ...

We study the class of standardly stratified alge- bras introduced by Cline, Parshall and Scott, and its subclass of the so-called weakly properly stratified algebras, which generalizes the class of properly stratified ...

The problem of unitarization of representations of algebras generated by idempotents with linear relations is studied. Construction of non-unitarizable representations for some subintervals of continuous spectrum is ...

We give a classification of representations of the Kleinian 4-group up to weak equivalence.