Condition for inducing topology in a vector lattice by the order completion

Properties of an order topology in vector lattices and Boolean algebras are studied. The main result is the following: in a vector lattice or a Boolean algebra with the condition of “closure by one step” (a generalization of the well-known “regularity” property of Boolean algebras and K-spaces) the order topology is induced by the topology of its Dedekind completion. Bibliography: 4 titles. Translated fromProblemy Matematicheskogo Analiza, No. 16, 1997, pp. 204–207.     

Orders of intersections of sylowp-subgroups in finite groups

Using the classification of finite simple groups, we tackle problem 5.12 from the “Kourovka Notebook,” for G a finite group satisfying O_p=1 for any prime p. Supported by RFFR. Translated fromAlgebra i Logika, Vol. 36, No. 2, pp. 156–165, March–April, 1997.     

Minimal permutation representations of finite simple exceptional groups of typesE 6,E 7, andE 8

A minimal permutation representation of a group is its faithful permutation representation of least degree. We will find degrees and point stabilizers, as well as ranks, subdegrees, and double stabilizers, for groups of types E₆, E₇, and E₈. This brings to a close the study of minimal permutation representations of finite simple Chevalley groups. Supported by RFFR grant No. 93-01-01501, through the program “Universities of Russia,” and by grant No. RPC300 of ISF and the Government of Russia. Translated fromAlgebra i Logika, Vol. 36, No. 5, pp. 518–530, September–October, 1997.     

On certain spectral properties of a quadratic self-adjoint matrix pencil with dominating main diagonals

Sufficient conditions for the “separation of the spectrum” of a quadratic matrix pencil with self-adjoint coefficients are found. A criterion for the representability of a positive operator in a finite-dimensional space in the form of a matrix with dominating main diagonal in each orthonormal basis is obtained. Translated fromMatematicheskie Zametki, Vol. 61, No. 3, pp. 381–390, March, 1997. Translated by A. I. Shtern     

Integral characteristics in the inverse problem of magnetotelluric sounding

This article examines some aspects of the one-dimensional inverse problem of magnetotelluric sounding. A uniqueness theorem is proved in the presence ofS-surfaces. A numerical algorithm based on transformation formulas is proposed. This research was partially supported by Russian Foundation for Basic Research (grant No. 96-01-00410) and by the State Scientific-Technical Program “Future Information Technologies” (grant No. 0201.06.010). Translated from Chislennye Metody v Matematicheskoi Fizike, Moscow State University, pp. 53–66, 1998.     

A quantum analog of the Poincare-Birkhoff-Witt theorem

We reduce the basis construction problem for character Hopf algebras to a study of special elements, called “super-letters,” which are defined by Shirshov standard words. It is shown that character Hopf algebras having not more than finitely many “hard” super-letters share some of the properties of universal envelopings of finite-dimensional lie algebras. The background for our proofs is the construction of a filtration such that the associated graded algebra is obtained by iterating the skew polynomials construction, possibly followed with factorization. Supported by the National Society of Researchers, México (SNI, exp. 18740, 1997–2000) Translated fromAlgebra i Logika, Vol. 38, No. 4, pp. 476–507, July–August, 1999.     

Probabilistic verification of proofs in calculuses

We define a special kind of a probabilistically checkable proof system, namely, probabilistically checkable proof calculuses (PCP calculuses). A proof in such a calculus can be verified with sufficient confidence by examining only one random path in the proof tree, without reading the whole proof. The verification procedure just checks all applications of inference rules along the path; its running time is assumed to be polynomial in the theorem length. It is shown that the deductive power of PCP calculuses is characterized as follows: (i) the decision problem for theorems is in PSPACE for all PCP calculuses; and (ii) the mentioned problem is PSPACE-hard for some of the calculuses. Bibliography: 14 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 241, 1997, pp. 97–116 This research was supported in part by the Russian Foundation for Basic Research. Translated by E. Ya. Dintsin.     

An analytical study of the sensitivity of a discrete stochastic model for sales dynamics

We consider a discrete model for sales dynamics in the case of a stochastic model of the market. The model includes “fast” and “slow” components of the market situation described by a stochastic process of “white noise” type and the correlated stochastic process. By using an integral representation of the main characteristics of the Kalman filter, we obtain expressions for stochastic parameters of additional errors of the estimate that arise in the case where the characteristics of noises are inexact. We make an asymptotical analysis of these expressions and give recommendations for the price-forming strategy in the case of uncertainty of the market situation. Bibliography: 2 titles. Translated fromObchyslyuval'na ta Prykladna Matematyka, No. 81, 1997, pp. 110–116.     

Computable classes of constructivizations of 2-constructivizable models

It is known that a class of constructivizations of a nonautostable 2-constructivizable model is infinite. Whether that class is effectively infinite or at least noncomputable is still not known, though there are grounds to believe that it is effectively infinite. Here, we argue for the effective infinity of a class of constructivizations of a nonautostable 2-constructivizable model which is not 1-prime in any finite enrichment by constants. Supported by RFFR grant No. 99-01-00485, by the Federal Research Program (FRP) “Integration,” and by the Program “Universities of Russia. Fundamental Research”. Translated fromAlgebra i Logika, Vol. 38, No. 6, pp. 697–722, November–December, 1999.     

Undecidability of a simple fragment of a positive theory with a single constant for a free semigroup of rank two

In the paper we study the algorithmic nature of some “simple” fragments of positive theories with “few” constants for free noncyclic semigroups. Translated fromMatematicheskie Zametki, Vol. 67, No. 2, pp. 191–200, February, 2000.     

Extension by zero of functions of several variables

We obtain sufficient conditions on a domainG ⊂ ℝn for functions defined onG to be extendable by zero to the entire space ℝn with smoothness preserved in an integral norm. Translated fromMatematicheskie Zametki, Vol. 64, No. 3, pp. 351–365, September, 1998. This research was supported by the Russian Foundation for Basic Research under grant No. 96-01-00243 and by program “Leading Science Schools” under grant No. 96-15-96102.     

Justification of a construction of the solution of the problem on a point source ofSH waves in a layered medium with vertical boundary

The solution is determined by the method of separation of variables. The method is justified by using a suitable space of generalized functions. Boundary conditions “are hidden” in this space. Bibliography: 5 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 218, 1994, pp. 56–66. Original article This work was supported by the Russian Foundation of Fundamental Research (Grant No. 93-011-16148). Translated by T. N. Surkova.     

The effective action and the spectrum of collective modes in the antiferromagnetic phase of the three-band repulsive hubbard model

The paper is concerned with the application of path integration (successive integration over “fast” and “slow” variables and the Hubbard-Stratonovich transformation) to the antiferromagnetic state in the three-band, two-dimensional repulsive Hubbard model. It is shown that, in the lowest approximation, the model under consideration is equivalent to the half-filled single-band Hubbard model. The effective action for the collective Bose-fields, the critical temperature of the phase transition, and the spectra of excitations are obtained. Bibliography: 24 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 245, 1997, pp. 216–230. Translated by C. L. Malyshev.     

The linearized equations of propagation of elastic perturbations in a body with free strains

For a stressed isotropic Murnaghan body with free (“intrinsic”) strains we decluce the equations of propagation of small elastic perturbations in terms of the free strain tensors and the gradient of the displacement. The latter characterizes the total strain, that is, the nonlinear superposition of the free and elastic strains. We write out separately the equations for the case of a spherical free strain tensor. Translated fromMatematichni Metodi ta Fiziko-Mekhanichni Polya, Vol. 40, No. 2, 1997, pp. 76–82.     

Inverse problem of magnetotelluric sounding in a medium with faults

This article considers a method for solving the direct and the inverse problems in the presence ofH-polarization for the fundamental three-layer model of deep magnetotelluric sounding with vertical tectonic faults and horizontal high-conductivityS-layers in a poorly conducting crystalline matrix. The conductivities may vanish on parts of the vertical cracks or the horizontalS-layers, i.e., in this modelS-layers and vertical faults may degenerate into an insulator. This research was partially supported by the Russian Foundation for Basic Research (grant No. 96-95-64340) and by the State Scientific-Technical Program “Future Information Technologies” (grant No. 0201.06.010). Translated from Chislennye Metody v Matematicheskoi Fizike, Moscow State University, pp. 53–66, 1998.     

Polynomiality criterion for entire functions of several complex variables

The “radial” polynomiality criterion for entire functions of several complex variables is proved. Translated fromMatermaticheskie Zametki, Vol. 66, No. 4, pp. 500–502, October, 1999.     

A problem with directional derivative in the theory of galvanomagnetic effects

We construct an asymptotics of the solution the Laplace equation in a “long” rectangle with the directional derivative given on its “long sides” and Dirichlet data on its “short sides.” By using the asymptotics, we calculate one of the integral characteristics, namely, the magnetoresistance. We obtain new formulas for the low-magnetic field magnetoresistance. Translated fromMatematicheskie Zametki, Vol. 65, No. 4, pp. 520–532, April, 1999.     

Direct problem of calculating the magnetic dipole field in a quasilayered medium

A method is developed for calculating the electromagnetic field of a magnetic dipole in a quasilayered two-dimensional medium. The quasi-three-dimensional problem is reduced to a two-dimensional problem for the Fourier-transformed electromagnetic field. An equivalent system of integral equations on the layer boundaries is obtained. This research was partially supported by the State Scientific-Technical Program “Future Information Technologies” (grant No. 0201.06.010) and the Interuniversity Scientific Program “Russian Universities: Basic Research.” Translated from Chislennye Metody v Matematicheskoi Fizike, Moscow State University, pp. 94–110, 1998.     

Large hyperbolic lattices

For a fundamental group of a compact orientable manifold, a condition is specified that is sufficient to guarantee the presence of a “virtual” epimorphism onto a free non-Abelian group. A consequence is deriving a strong Tits alternative. An arbitrary noncompact finitely generated discrete subgroup in PO(3, 1) either is large or is virtually Abelian. An application is provided to the problem of uniform exponential growth for lattices in a 3-dimensional hyperbolic space and of growth of Betti numbers for lattices in a hyperbolic n-dimensional space, where n is an odd number. Supported by RFBR (project No. 08-01-00067), by DFG grant Gr 627-11, and by Forschergruppe “Spektrale Analysis, asymptotical Verteilungen und stochastische Dynamiken,” Billfold University. (G. A. Noskov) Translated from Algebra i Logika, Vol. 48, No. 2, pp. 174–189, March–April, 2009.