On the independence of optimal boundary controls of string vibrations on the choice of the coordination point of initial and terminal conditions

We establish that the optimal boundary controls of string vibrations found in the papers published in Differentsial’nye Uravneniya, 2007, vol. 43, nos. 10–12 and 2008, vol. 44, no. 1 preserve their form if an arbitrary point of the string is taken as the point where the initial and terminal conditions are coordinated.     

On the theory of motion of nonholonomic systems. The reducing-multiplier theorem

This classical paper by S.A. Chaplygin presents a part of his research in non-holonomic mechanics. In this paper, Chaplygin suggests a general method for integration of the equations of motion for non-holonomic systems, which he himself called the “reducing-multiplier method”. The method is illustrated on two concrete problems from non-holonomic mechanics. This paper produced a considerable effect on the further development of the Russian non-holonomic community. With the help of Chaplygin’s reducing-multiplier theory the equations for quite a number of non-holonomic systems were solved (such systems are known as Chaplygin systems). First published about a hundred years ago, this work has not lost its scientific significance and is hoped to be estimated at its true worth by the English-speaking world. This publication contributes to the series of RCD translations of Chaplygin’s scientific heritage. In 2002 we published two of his works (both cited in this one) in the special issue dedicated to non-holonomic mechanics (RCD, Vol. 7, no. 2). These translations along with translations of his other two papers on hydrodynamics (RCD, Vol. 12, nos. 1,2) aroused considerable interest and are broadly cited by modern researches. Originally published in: Matematicheskiĭ sbornik (Mathematical Collection), 1911, vol. 28, issue 1. The content of §§ 2 and 3 of this study was presented at the session of the Moscow Mathematical Society on December 11, 1906.     

Stochastic modeling of the growth process

In this paper we estimate the upper boundary of the number of trees in the selection stand determined for harvesting in a future. At the same time we showed that the present resource of the number of trees in selection stand is sustained. This is achieved by stochastic modeling of the number of trees and the number of felled trees and by solving the partial differential equation. The same problem is solved in the papers, Mitrović (Stochastic modeling of the number of trees and the number of felled trees in selection stands, YUJOR, vol 14(1), pp 57–64, 2004; Stochastic modeling of the number of felled trees in selection stands, Computational and Applied Mathematics, vol 24(2), pp 285–292, 2005). In this paper the modified mathematical model is represented.      

A nontrivial example of application of the Nielsen fixed-point theory to differential systems: Problem of Jean Leray

In reply to a problem posed by Jean Leray in 1950, a nontrivial example of application of the Nielsen fixed-point theory to differential systems is given. So the existence of two entirely bounded solutions or three periodic (harmonic) solutions of a planar system of ODEs is proved by means of the Nielsen number. Subsequently, in view of T. Matsuoka's results in Invent. Math. (70 (1983), 319-340) and Japan J. Appl. Math. (1 (1984), no. 2, 417-434), infinitely many subharmonics can be generically deduced for a smooth system. Unlike in other papers on this topic, no parameters are involved and no simple alternative approach can be used for the same goal.

     

Krein Systems and Canonical Systems on a Finite Interval: Accelerants with a Jump Discontinuity at the Origin and Continuous Potentials

This paper is devoted to connections between accelerants and potentials of Krein systems and of canonical systems of Dirac type, both on a finite interval. It is shown that a continuous potential is always generated by an accelerant, provided the latter is continuous with a possible jump discontinuity at the origin. Moreover, the generating accelerant is uniquely determined by the potential. The results are illustrated on pseudo-exponential potentials. The paper is a continuation of the earlier paper of the authors (Alpay et al. in Modern Analysis and Applications. The Mark Krein Centenary Conference, vol. 2, pp. 19–36, OT 191. Birkhäuser, Basel, 2009) dealing with the direct problem for Krein systems.     

Stepwise Gauge Equivalence of Differential Operators

In this paper, we study the relation between the notion of gauge equivalence and solutions of certain systems of nonlinear partial differential equations. This relation is based on stepwise gauge equivalence.__________Translated from Matematicheskie Zametki, vol. 77, no. 6, 2005, pp. 917–929.Original Russian Text Copyright ©2005 by S. P. Khekalo.     

The Ok Corral and the Power of the Law (A Curious Poisson-Kernel Formula for a Parabolic Equation)

Two lines of gunmen face each other, there being initially mon one side, n on the other. Each person involved is a hopelessshot, but keeps firing at the enemy until either he himselfis killed or there is no one left on the other side. Let µ(m,n) be the expected number of survivors. Clearly, we have boundaryconditions: We also have theequation This is because theprobability that the first successful shot is made by the sidewith m gunmen is m/(m + n). On using the recurrence relation(1.2) together with the boundary condition (1.1), the computerproduces Table 1 below, in which 1991 Mathematics Subject Classification 60F05.     

Higher cohomology of parabolic actions on certain homogeneous spaces

We show that for a parabolic R ^d -action on PSL(2,R) ^d /Γ, the cohomologies in degrees 1 through d ? 1 trivialize, and we give the obstructions to solving the degree-d coboundary equation, along with bounds on Sobolev norms of primitives. In previous papers, we have established these results for certain Anosov systems. This work extends the methods of those papers to systems that are not Anosov. The main new idea is defining special elements of representation spaces that allow us to modify the arguments from the previous papers. We discuss how to generalize this strategy to R ^d -systems coming from a product of Lie groups, as in the systems analyzed here.     

Some aspects of the nontrivial solvability of homogeneous Dirichlet problems for linear equations of arbitrary even order in the disk

In this paper, we obtain a necessary and sufficient condition for the nontrivial solvability of homogeneous Dirichlet problems in the disk for linear equations of arbitrary even order 2m with constant complex coefficients and homogeneous nondegenerate symbol in general position. The cases m=1, 2, 3 are studied separately. For the case m=2, we consider examples of real elliptic systems reducible to single equations with constant complex coefficients for which the homogeneous Dirichlet problem in the disk has a countable set of linearly independent polynomial solutions.Translated from Matematicheskie Zametki, vol. 77, no. 4, 2005, pp. 498–508.Original Russian Text Copyright © 2005 by V. P. Burskii, E. A. Buryachenko.This revised version was published online in April 2005 with a corrected issue number.     

The Number of Edge Colorings with no Monochromatic Cliques

Let F(n,r,k) denote the maximum possible number of distinctedge-colorings of a simple graph on n vertices with r colorswhich contain no monochromatic copy of K_k. It is shown thatfor every fixed k and all n>n₀(k), and , where t_k–1(n)is the maximum possible number of edges of a graph on n verticeswith no K_k (determined by Turán's theorem). The caser=2 settles an old conjecture of Erds and Rothschild, whichwas also independently raised later by Yuster. On the otherhand, for every fixed r>3 and k>2, the function F(n,r,k)is exponentially bigger than . The proofs are based on Szemerédi's regularity lemmatogether with some additional tools in extremal graph theory,and provide one of the rare examples of a precise result provedby applying this lemma.     

Localization of the essential spectrum of the energy operators ofn-particle quantum systems in a magnetic field

Theorems on the localization of the essential spectrum of givenSO(2) symmetry forn-particle Hamiltonians in an external magnetic field are proved. The energy operators are studied for systems of arbitrary particles in the absence of an external potential field and for systems of identical particles in an external potential field. Some of the results were announced in earlier papers [1,2].Radiophysics Research Institute. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 97, No.1, pp. 94–112, October, 1993.     

A Consistent Estimator of the Entropy of Measures and Dynamical Systems

In the paper, a new invariant of measures and dynamical systems, called statentropy, is described. A statistical estimator for statentropy, computed without using auxiliary estimates of measures, is constructed. It is proved that the proposed statistical estimator is consistent under fairly general restrictions. We show that for exact dimensional measures, statentropy coincides with the Hausdorff dimension of the measure, and for ergodic dynamical systems, it coincides with the metric entropy of the map.__________Translated from Matematicheskie Zametki, vol. 77, no. 6, 2005, pp. 903–916.Original Russian Text Copyright ©2005 by E. A. Timofeev.     

Translation invariant valuations in the space of planes

The paper is related to the problem of measure generation in the space IE of planes in IR ³ by combinatorial, translation invariant valuations. General results concerning that problem have been derived in 1994 and 1996 (this journal vol. 31, no. 4. and vol. 33, no. 4, respectively). The purpose of the present article is to give a proof of two geometrical identities on which the theorem on valuations in the space IE can be based. The article consists of the motivational first part that contains the basic concepts from the theory of combinatorial valuations and measure generation in IE, and the second that gives a proof of the identities in question.     

On the Index of Vector Fields Tangent to Hypersurfaces with Non-Isolated Singularities

Let F be a germ of a holomorphic function at 0 in Cⁿ⁺¹, having0 as a critical point not necessarily isolated, and let be a germ of a holomorphic vectorfield at 0 in Cⁿ⁺¹ with an isolated zero at 0, and tangent toV := F^–1(0). Consider the O_V,0-complex obtained by contractingthe germs of Kähler differential forms of V at 0 (0.1) with the vector field X:=|_Von V: (0.2)     

Localization of Closed (or Periodic) Solutions of a Differential System with Concave Nonlinearities

Consider a scalar differential equation , where I is an open interval containing [0,T]. Assumethat f(t, x) is continuous with a continuous derivative , and weakly concave (or weakly convex)in x for all t I, though strictly concave (or strictly convex)for some t [0, T]. It is well known that in this case therecan be either no, one or two closed solutions; that is, solutions(t) for which (0) = (T) If there are two closed solutions, thenthe greater has a negative characteristic exponent and the smallerhas a positive one. It is easily seen that this is equivalentto a statement on localization of closed solutions. It is shownhow this statement can be generalized to systems of differentialequations . The requirements are that the coordinate functions ) be continuous with continuous derivatives with respect to x₁,x₂, ...,x_n, that the f_j are weakly concave (or weakly convex)in , and that a certain condition pertaining to strict concavity (or strict convexity) is fulfilled.2000 Mathematics Subject Classification 34C25, 34C12.     

A Blichfeldt-type inequality for the surface area

In 1921, Blichfeldt gave an upper bound on the number of integral points contained in a convex body in terms of the volume of the body. More precisely, he showed that #(K?\Bbb Zⁿ) ￡ n! vol(K)+n\#(K\cap{\Bbb Z}^n)\le n! {\rm vol}(K)+n , whenever K ì \Bbb RⁿK\subset{\Bbb R}^n is a convex body containing n + 1 affinely independent integral points. Here we prove an analogous inequality with respect to the surface area F(K), namely #(K?\Bbb Zⁿ) < vol(K) + ((?n+1)/2) (n-1)! F(K)\#(K\cap{\Bbb Z}^n) < {\rm vol}(K) + ((\sqrt{n}+1)/2) (n-1)! {\rm F}(K) . The proof is based on a slight improvement of Blichfeldt’s bound in the case when K is a non-lattice translate of a lattice polytope, i.e., K = t + P, where t ? \Bbb Rⁿ\\Bbb Zⁿt\in{\Bbb R}^n\setminus{\Bbb Z}^n and P is an n-dimensional polytope with integral vertices. Then we have #((t+P)?\Bbb Zⁿ) ￡ n! vol(P)\#((t+P)\cap{\Bbb Z}^n)\le n! {\rm vol}(P) . Moreover, in the 3-dimensional case we prove a stronger inequality, namely #(K?\Bbb Zⁿ) < vol(K) + 2 F(K)\#(K\cap{\Bbb Z}^n)< {\rm vol}(K) + 2 {\rm F}(K) .     

On some statistical properties of the “Book Stack” transformation

This paper is devoted to studying the statistical properties of the “Book Stack” transformation proposed by B.Ya. Ryabko (Probl. Inf. Transm., 1980, vol. 16, no. 4) as a data compression method. The same transformation has been used by Ryabko and A.I. Pestunov (Probl. Inf. Transm., 2004, vol. 40, no. 1) to construct the similarly named statistical test. This test is designed for the verification of the null hypothesis that an available input i.i.d. sample corresponds to a discrete uniform distribution with a known support. They propose to verify this hypothesis for a new sample obtained via the Book Stack transformation instead of the input sample. This gives rise to the natural problem of comparing the results given by the same statistical test in the application to input and output samples. If the null hypothesis is true, these procedures prove to be equivalent; however, this is actually not the case anymore when there are some violations of this hypothesis. The results of comparing the criteria surely depend on the class of the alternatives considered. This paper deals with the natural alternative consisting of the fact that the initial replicated sample corresponds to a discrete, albeit, nonuniform, distribution with a fixed support. It has been demonstrated that some standard criteria for the verification of the null hypothesis prove to be more powerful for an input sample in comparison with a transformed sample. In particular, this takes place for the likelihood ratio criterion and (with some formal constraints) the χ²-criterion.     

Hilbert and Hilbert—Samuel polynomials and partial differential equations

Systems of linear partial differential equations with constant coefficients are considered. The spaces of formal and analytic solutions of such systems are described by algebraic methods. The Hilbert and Hilbert—Samuel polynomials for systems of partial differential equations are defined.Translated from Matematicheskie Zametki, vol. 77, no. 1, 2005, pp. 141–151.Original Russian Text Copyright © 2005 by A. G. Khovanskii, S. P. Chulkov.This revised version was published online in April 2005 with a corrected issue number.     

Moduli problem and points on some twisted Shimura varieties of PEL type

In this article we describe the moduli problem of a “twist” of some simple Shimura varieties of PEL type that appear in Kottwitz's papers [R. Kottwitz, Shimura varieties and λ-adic representations, in: Automorphic Forms, Shimura Varieties and L-Functions, part 1, in: Perspect. Math., vol. 10, Academic Press, San Diego, CA, 1990, pp. 161-209; R. Kottwitz, Points on some Shimura varieties over finite fields, J. Amer. Math. Soc. 5 (2) (1992) 373-444] and [R. Kottwitz, On the λ-adic representations associated to some simple Shimura varieties, Invent. Math. 108 (1992) 653-665] and then, using the moduli problem, we compute the cardinality of the set of points over finite fields of the twisted Shimura varieties. Using this result, we compute the zeta function of the twisted varieties. The twist of the Shimura varieties is done by a mod q representation of the absolute Galois group of the reflex field of the Shimura varieties.     

A computational procedure on higher‐dimensional nilsolitons

In this paper, we develop algorithmic approach to classify nilsoliton metrics on dimension 8. This approach includes finding eigenvalue type of the nilsoliton derivation, the nullity type, the index of the algebra. It can be considered as a continuation of our papers in Abstract and Applied analysis, volume 2013, 1 to 7, (2013), with article ID 871930, and in Journal of Symbolic Computation 50 (2013), 350 ‐ 373. In our previous work, we classified only ordered type, nilsoliton metric Lie algebras ie, the algebras with the derivation type (1 < 2 < 3… < n) in dimension 8 and 9. Here, we consider more general case. We consider such metrics with simple derivations on an indecomposable nilpotent Lie algebra. In one of our previous study, we have already classified nilsoliton metric Lie algebras with nonsingular Gram matrix in dimension 8 in Journal of Symbolic Computation, vol: 50, 350 ‐ 373, 2013. Here, we focus on the metrics with singular Gram matrix. We also develop faster algorithm in classifying such metrics.