Vol 101, No 3-4 (2017)

Following A. I.Mal’tsev, we say that a group G has finite general rank if there is a positive integer r such that every finite set of elements of G is contained in some r-generated subgroup. Several known theorems concerning finitely generated residually finite groups are generalized here to the case of residually finite groups of finite general rank. For example, it is proved that the families of all finite homomorphic images of a residually finite group of finite general rank and of the quotient of the group by a nonidentity normal subgroup are different. Special cases of this result are a similar result of Moldavanskii on finitely generated residually finite groups and the following assertion: every residually finite group of finite general rank is Hopfian. This assertion generalizes a similarMal’tsev result on the Hopf property of every finitely generated residually finite group.

We construct a probabilistic representation for the generalized solution of the Cauchy problem for the system of strongly coupled nonlinear parabolic equations describing the growth of cells under contact inhibition.

The aim of this paper is to establish the boundedness of certain sublinear operators with rough kernel generated by Calderón–Zygmund operators and their commutators on generalized Morrey spaces under generic size conditions which are satisfied by most of the operators in harmonic analysis. The Marcinkiewicz operator which satisfies the conditions of these theorems can be considered as an example.

Alternative (right) Noetherian algebras are considered. It is proved that, in these algebras, the nil ideals of finite codimension are nilpotent, which generalizes the corresponding Zhevlakov’s result. As a corollary, we describe just infinite alternative nonassociative algebras (for the field characteristic distinct from 2).

The notions of almost ω-categoricity and 1-local ω-categoricity are studied. In particular, necessary and sufficient conditions for their equivalence under additional assumptions are found. It is proved that 1-local ω-categorical theories on dense linear orders are Ehrenfeucht and that Ehrenfeucht quite o-minimal binary theories are almost ω-categorical.

Regularization of the Bose–Einstein distribution using a parastatistical correction, i.e., by means of the Gentile statistics, is carried out. It is shown that the regularization result asymptotically coincides with the Erdős formula obtained by using Ramanujan’s formula for the number of variants of the partition of an integer into summands. TheHartley entropy regarded as the logarithm of the number of variants defined by Ramanujan’s exact formula asymptotically coincides with the polylogarithm associated with the entropy of the Bose–Einstein distribution. The fact that these formulas coincide makes it possible to extend the entropy to the domain of the Fermi–Dirac distribution with minus sign. Further, the formulas for the distribution are extended to fractional dimension and also to dimension 1, which corresponds to the Waring problem. The relationship between the resulting formulas and the liquid corresponding to the case of nonpolar molecules is described and the law of phase transition of liquid to an amorphous solid under negative pressure is discussed. Also the connection of the resulting formulas with the gold reserve in economics is considered.

We obtain some specific exponential lower bounds for the chromatic numbers of distance graphs with large girth.

In this paper, we obtain five tests (three of which are symmetric) of pointwise convergence of Fourier series with respect to generalized Haar systems; the tests are similar to the Dini convergence tests. It is shown that the Dini convergence tests for Price systems are also valid for generalized Haar systems. It is also shown that the classicalDini convergence test does not apply, in general, even to generalized Haar systems, although the classical symmetric Dini test for generalized Haar systems is valid. Also upper bounds for the Dirichlet kernels for generalized Haar systems are obtained.

Let u ≢ −∞be a subharmonic function in the complex plane. We establish necessary and/or sufficient conditions for the existence of a nonzero entire function f for which the modulus of the product of each of its kth derivative k = 0, 1,..., by any polynomial p is not greater than the function Ce^u in the entire complex plane, where C is a constant depending on k and p. The results obtained significantly strengthen and develop a number of results of Lars Hörmander (1997).

We use the notion of triples D⁺ → H → D⁻ of Hilbert spaces to develop an analog of the Friedrichs extension procedure for a class of nonsemibounded operator matrices. In addition, we suggest a general approach (stated in the same terms) to the construction of variational principles for the eigenvalues of such matrices.

In this article, we study, from the mathematical point of view, the analogies between language and multi-particle systems in thermodynamics. We attempt to introduce an appropriate mathematical apparatus and the technical tools of statistical physics to descriptions of language. In particular, we apply the notions of number of degrees of freedom, Bose condensate, phase transition and others to linguistics objects. On the basis of a statistical analysis of dictionaries and statistical distributions in languages, we conjecture that the transition from the semiotic communication system of the higher primates to human language can be described as a phase transition of the first kind. We show that the number of words appearing with frequency 1 in a corpus of texts is equal to the number of ones in the corresponding Fermi–Dirac distribution, while the high frequency of stop-words corresponds to the large number of particles in the Bose condensate, when the number of degrees of freedom is less than two, provided there is a gap in the spectrum. The presented considerations are illustrated by examples from the Russian language. Some of the illustrative examples are untranslatable into English, and so they were replaced in translation by similar examples from the English language.

A discrete dynamical system generated by a diffeomorphism f on a compact manifold is considered. The Morse spectrum is the limit set of Lyapunov exponents of periodic pseudotrajectories. It is proved that the Morse spectrum coincides with the set of averagings of the function ϕ(x, e) = ln|Df(x)e| over the invariant measures of the mapping induced by the differential Df on the projective bundle.

In the present paper,we describe conditions on a vector group C which are necessary and sufficient for the class of completely decomposable torsion-free Abelian groups to be a _CEH-class.

Some results about the nonexistence of nontrivial nonnegative solutions for some classes of nonlinear partial differential inequalities containing nonintegral powers of the Laplace operator are obtained.

We study Fourier series of Jacobi polynomials P_k^α−r,−r (x), k = r, r +1,..., orthogonal with respect to the Sobolev-type inner product of the following form: \(\left\langle {f,g} \right\rangle = \sum\limits_{v = 0}^{r - 1} {{f^{\left( v \right)}}} \left( { - 1} \right){g^{\left( v \right)}}\left( { - 1} \right) + \int_{ - 1}^1 {{f^{\left( r \right)}}} {g^{\left( r \right)}}\left( t \right){\left( {1 - t} \right)^\alpha }dt\). It is shown that such series are a particular case of mixed series of Jacobi polynomials P_k^α,β(x), k = 0, 1,..., considered earlier by the author. We study the convergence of mixed series of general Jacobi polynomials and their approximation properties. The results obtained are applied to the study of the approximation properties of Fourier series of Sobolev orthogonal Jacobi polynomials P_k^α−r,−r (x).