Том 57, № 1 (2016)

We consider graphs whose edges are marked by numbers (weights) from 1 to q - 1 (with zero corresponding to the absence of an edge). A graph is additive if its vertices can be marked so that, for every two nonadjacent vertices, the sum of the marks modulo q is zero, and for adjacent vertices, it equals the weight of the corresponding edge. A switching of a given graph is its sum modulo q with some additive graph on the same set of vertices. A graph on n vertices is switching separable if some of its switchings has no connected components of size greater than n - 2. We consider the following separability test: If removing any vertex from G leads to a switching separable graph then G is switching separable. We prove this test for q odd and characterize the set of exclusions for q even. Connection is established between the switching separability of a graph and the reducibility of the n-ary quasigroup constructed from the graph.

We complete the description of 3-filiform Leibniz algebras of maximum length. Moreover, using the good structure of algebras of maximum length, we study some of their cohomological properties. Our main tools are the previous results by Cabezas and Pastor [1], the construction of an appropriate homogeneous basis in the considered connected gradation and the computational support provided by two programs implemented in Mathematica.

We consider G-invariant affinor metric structures and their particular cases, sub-Kähler structures, on a homogeneous space G/H. The affinor metric structures generalize almost Kähler and almost contact metric structures to manifolds of arbitrary dimension. We consider invariant sub-Riemannian and sub-Kähler structures related to a fixed 1-form with a nontrivial radical. In addition to giving some results for homogeneous spaces of arbitrary dimension, we study these structures separately on the homogeneous spaces of dimension 4 and 5.

We obtain a sufficient solvability condition for Cauchy problems for a polynomial difference operator with constant coefficients. We prove that if the generating function of the Cauchy data of a homogeneous Cauchy problem lies in one of the classes of Stanley’s hierarchy then the generating function of the solution belongs to the same class.

We study the abelian normal divisors of soluble matrix groups.

Construction of multiplicative functions and Prym differentials, including the case of characters with branch points, reduces to solving a homogeneous boundary value problem on the Riemann surface. The use of the well-established theory of boundary value problems creates additional possibilities for studying Prym differentials and related bundles. Basing on the theory of boundary value problems, we fully describe the class of divisors of Prym differentials and obtain new integral expressions for Prym differentials, which enable us to study them directly and, in particular, to study their dependence on the point of the Teichmüller space and characters. Relying on this, we obtain and generalize certain available results on Prym differentials by a new method.

We consider the functions periodic at infinity with values in a complex Banach space. The notions are introduced of the canonical and generalized Fourier series of a function periodic at infinity. We prove an analog of Wiener’s Theorem on absolutely convergent Fourier series for functions periodic at infinity whose Fourier series are summable with weight. The two criteria are given: for the function periodic at infinity to be the sum of a purely periodic function and a function vanishing at infinity and for a function to be periodic at infinity. The results of the article base on substantially use on spectral theory of isometric representations.

We prove that if a periodic Shunkov group is saturated with degree 2 general linear groups over finite fields then it is isomorphic to the degree 2 general linear group over a suitable locally finite field.