Том 99, № 3-4 (2016)

The properties of topological entropy as a function on a compact family of maps of a compact metric space are studied.

We study an operator which is the composition of the convolution operator and the operator of multiplication by a fixed entire function. Such operators find applications in the Fisher expansion problem, the Cauchy problem for convolution operators, etc.

For any γ ∈ (0, 1) and ε > 0, we construct a cylindrical cascade with a γ-Hölder function over some rotation of the circle. This transformation has the Besicovitch property; i.e., it is topologically transitive and has discrete orbits. The Hausdorff dimension of the set of points of the circle that have discrete orbits is greater than 1 − γ − ε.

Let S be a bielliptic surface over a finite field, and let an elliptic curve B be the Albanese variety of S; then the zeta function of the surface S is equal to the zeta function of the direct product P¹ × B. Therefore, the classification problem for the zeta functions of bielliptic surfaces is reduced to the existence problem for surfaces of a given type with a given Albanese curve. In the present paper, we complete this classification initiated in [1].

In the paper, it is proved that, if f(x₁,..., x_n)g(y₁,..., y_m) is a multilinear central polynomial for a verbally prime T-ideal Γ over a field of arbitrary characteristic, then both polynomials f(x₁,..., x_n) and g(y₁,..., y_m) are central for Γ.

Generalized boundary conditions on multilayer films bounding a half-space and consisting of alternating infinitely thin strongly and weakly permeable layers are derived. The solution of the problem for the Laplace equation in a half-plane D bounded by a three-layer film is expressed in simple quadratures in terms of the solution of the classical Dirichlet problem in D without a film.

The well-known extremal problem on hypergraph colorings is studied. We investigate whether it is possible to color a hypergraph with a fixed number of colors equitably, i.e., so that, on the one hand, no edge is monochromatic and, on the other hand, the cardinalities of the color classes are almost the same. It is proved that if H = (V,E) is a simple hypergraph in which the least cardinality of an edge equals k, |V| = n, r|n, and

\(\sum\limits_{e \in E} {{r^{1 - \left| e \right|}}} \leqslant c\sqrt k ,\)

Bounds for the multiplicity of the eigenvalues of the Sturm–Liouville problem on a graph, which are valid for a wide class of consistency (transmission) conditions at the vertices of the graph, are given. The multiplicities are estimated using the topological characteristics of the graph. In the framework of the notions that we use, the bounds turn out to be exact.

The limit probabilities of first-order properties of a random graph in the Erdős–Rényi model G(n, n^−α), α ∈ (0, 1), are studied. For any positive integer k ≥ 4 and any rational number t/s ∈ (0, 1), an interval with right endpoint t/s is found in which the zero-one k-law holds (the zero-one k-law describes the behavior of the probabilities of first-order properties expressed by formulas of quantifier depth at most k).Moreover, it is proved that, for rational numbers t/s with numerator not exceeding 2, the logarithm of the length of this interval is of the same order of smallness (as n→∞) as that of the length of the maximal interval with right endpoint t/s in which the zero-one k-law holds.

Estimates of quantities characterizing the complexity of the family of convex subsets of the d-dimensional cube [1, n]^d as n→∞ are given. The geometric properties of spaces with norm generated by the generalized majorant of partial sums are studied.

The Goursat problem for the fractional telegraph equation with Caputo derivatives is studied. An existence and uniqueness theorem for the solution of the problem is proved.

The quality of approximation by Fourier means generated by an arbitrary generator with compact support in the spaces L_p, 1 ≤ p ≤ +∞, of 2π-periodic pth integrable functions and in the space C of continuous 2π-periodic functions in terms of the generalized modulus of smoothness constructed froma 2π-periodic generator is studied. Natural sufficient conditions on the generator of the approximation method and values of smoothness ensuring the equivalence of the corresponding approximation error and modulus are obtained. As applications, Fourier means generated by classical kernels as well as the classical moduli of smoothness are considered.

The class of one-dimensional quasilattices parametrized by translations of the torus is studied. The trigonometric integrals averaging the moduli of trigonometric sums related to quasilattices are considered for this class. Nontrivial estimates of such integrals are obtained. The relationship between trigonometric integrals and several problems in the theory of Diophantine approximations is discussed.