erratum

Abstract— In the paper, the elementary net closure problem is considered. An elementary net (net without a diagonal) σ = (σij)i ≠ j of additive subgroups σij of field k is called “closed” if elementary net group E(σ) does not contain new elementary transvections. Elementary net σ = (σij) is called “supplemented” if table (with a diagonal) σ = (σij), 1 ≤ i, j ≤ n, is a (full) net for some additive subgroups

Abstract Homological properties of quotient divisible Abelian groups are studied. These groups form an important class of groups, which has been extensively studied in recent years. The first part of the paper is devoted to conditions for the triviality of extension groups in which one of the arguments is a quotient divisible group. Under certain additional assumptions, groups of homomorphisms from

Abstract The initial-value problem (the Cauchy problem) for an ordinary differential equation of the first order is considered. It is assumed that the right-hand side of the equation is a continuous function defined on a set consisting of a connected open set (a domain) of the two-dimensional Euclidean space, as well as on part of its boundary. It is known that, for any point of the domain, the Peano

Abstract Finite quasi-groups without sub-quasi-groups are considered. It is shown that polynomially complete quasi-groups with this property are quasi-primal. The case in which the automorphism groups act transitively on these quasi-groups is considered. Quasi-groups of prime-power order defined on an arithmetic vector space over a finite field are also studied. Necessary conditions for a multiplication

Abstract The notion of a supercharacter theory was proposed by P. Diaconis and I.M. Isaacs in 2008. A supercharacter theory for a given finite group is a pair of the system of certain complex characters and the partition of group into classes that have properties similar to the system of irreducible characters and the partition into conjugacy classes. In the present paper, we consider the group obtained

Abstract This paper presents a brief survey for the theory of stability of weakly hyperbolic invariant sets. It has been proved in several papers that I published along with Pliss and Sell that a weakly hyperbolic invariant set is stable even if the Lipschitz condition fails to hold. However, the uniqueness of leaves of a weakly hyperbolic invariant set of a perturbed system remains an open question

Abstract This paper contains an explanation of Ramanujan-type formulas with cubic radicals of cubic irrationalities in the situation when these radicals are contained in a pure cubic extension. We give a complete description of formulas of such type, answering the Zippel’s question. It turns out that Ramanujan-type formulas are in some sense unique in this situation. In particular, there must be no

Abstract A computational approach to detecting Andronov–Hopf bifurcations in polynomial systems of ordinary differential equations depending on parameters is proposed. It relies on algorithms of computational commutative algebra based on the Groebner bases theory. The approach is applied to the investigation of two models related to the double phosphorylation of mitogen-activated protein kinases, a

Abstract The present communication is devoted to the construction of monotone difference schemes of the second order of local approximation on non-uniform grids in space for 2D quasi-linear parabolic convection-diffusion equation. With the help of difference maximum principle, two-sided estimates of the difference solution are established and an important a priori estimate in a uniform norm C is proved

Abstract In this paper, we consider weak, directional and strong matrix majorizations. Namely, for square matrices A and B of the same size we say that A is weakly majorized by B if there is a row stochastic matrix X such that A = XB. Further, A is strongly majorized by B if there is a doubly stochastic matrix X such that A = XB. Finally, A is directionally majorized by B if Ax is majorized by Bx for

Abstract A two-dimensional periodic system of differential equations with two hyperbolic periodic solutions is considered. It is assumed that heteroclinic solutions lie at the intersection of stable and unstable manifolds of fixed points; more precisely, the existence of a heteroclinic contour is assumed. I study the case in which stable and unstable manifolds intersect nontransversally at the points

Abstract The main fields of application of formal groups are algebraic geometry and class field theory. The later uses both the classical Hilbert symbol (the norm-residue symbol) and its generalization. One of the most important problems is finding explicit formulas for various modifications of this symbol related to formal groups. There are two approaches to constructing formal groups (i.e., power

Abstract In this paper, an automatic control discrete-time system of the second order is studied. The nonlinearity of this system satisfies the generalized Routh–Hurwitz condition. Systems of this type are widely used in solving modern applied problems of the theory of automatic control. This work is a continuation of the results of research presented in the paper “On the Problem of Aizerman: Coefficient

Abstract In this paper, various extensions of local fields are considered. For arbitrary finite extension K of the field of p-adic numbers, the maximum Abelian extension KAb/K and the corresponding Galois group can be described using the well-known Lubin–Tate theory. It is represented as a direct product of groups obtained using the maximum unramified extension of K and a fully ramified extension obtained

Abstract The problem of stability of the zero solution of a system with a “center”-type critical point at the origin of coordinates is considered. For the first time, such a problem for autonomous systems was investigated by A.M. Lyapunov. We continued Lyapunov’s investigations for systems with a periodic dependence on time. In this paper, systems with a quasi-periodic time dependence are considered

Abstract In this paper, we consider the problem of constructing c-optimal designs for polynomial regression without an intercept. The special case of c = f '(z) (i.e., the vector of derivatives of the regression functions at some point z is selected as vector c) is considered. The analytical results available in the literature are briefly reviewed. An effective numerical method for finding f '(z)-optimal

Abstract A matrix whose component are binomial coefficients and determinant was calculated earlier by L. Carlitz is investigated. It is shown that Carlitz matrix is the result of binomal specialization for dual Jacobi–Trudi determinant presentation of certain Schur function. It leads to another way to calculate Carlitz determinant based upon symmetric function theory. The eigenvalues of Carlitz matrix

Abstract Let Zi (i ≥ 1) be a sequence of independent and identically distributed random variables with standard exponential distribution H and let Z(n) (n ≥ 1) be the corresponding sequence of exponential records associated with Zi (i ≥ 1). Let us call the sequence Z(n) (n ≥ 1) the first “record derivative” of the sequence Zi (i ≥ 1). ν1 = Z(1). It is known that ν2 = Z(2) – Z(1), independent variables

Abstract Assume that n independent uniformly distributed random points are set on the unit circle. Construct the convex random polygon with vertices in these points. What are the average area and the average perimeter of this polygon? Brown computed the average area several years ago. We compute the average perimeter and obtain quite similar expressions. We also discuss the rate of the convergence