Stability of nonautonomous difference equations with several delays

We consider the possibility to construct efficient stability criteria for solutions to difference equations with variable coefficients. We prove that one can associate a difference equation with a certain functional differential equation, whose solution has the same asymptotic behavior. We adduce examples, demonstrating the essential character of conditions of the obtained theorems and the exactness of the constant 3/2 which defines the boundary of the stability domain.     

Singular Sturmian separation theorems for nonoscillatory symplectic difference systems

ABSTRACT

In this paper, we derive new singular Sturmian separation theorems for nonoscillatory symplectic difference systems on unbounded intervals. The novelty of the presented theory resides in two aspects. We introduce the multiplicity of a focal point at infinity for conjoined bases, which we incorporate into our new singular Sturmian separation theorems. At the same time we do not impose any controllability assumption on the symplectic system. The presented results naturally extend and complete the known Sturmian separation theorems on bounded intervals by J. V. Elyseeva [Comparative index for solutions of symplectic difference systems, Differential Equations 45(3) (2009), pp. 445–459, translated from Differencial'nyje Uravnenija 45 (2009), no. 3, 431–444], as well as the singular Sturmian separation theorems for eventually controllable symplectic systems on unbounded intervals by O. Do?lý and J. Elyseeva [Singular comparison theorems for discrete symplectic systems, J. Difference Equ. Appl. 20(8) (2014), pp. 1268–1288]. Our approach is based on developing the theory of comparative index on unbounded intervals and on the recent theory of recessive and dominant solutions at infinity for possibly uncontrollable symplectic systems by the authors [P. ?epitka and R. ?imon Hilscher, Recessive solutions for nonoscillatory discrete symplectic systems, Linear Algebra Appl. 469 (2015), pp. 243–275; P. ?epitka and R. ?imon Hilscher, Dominant and recessive solutions at infinity and genera of conjoined bases for discrete symplectic systems, J. Difference Equ. Appl. 23(4) (2017), pp. 657–698]. Some of our results, including the notion of the multiplicity of a focal point at infinity, are new even for an eventually controllable symplectic difference system.     

Difference inequalities generated by impulsive parabolic differential-functional problems

The paper deals with parabolic differential-functional equations. Initial-boundary value problems are considered with impulses given in fixed points. We prove theorems on difference-functional impulsive inequalities generated by original problems.Explicit finite difference schemes are used to approximate the solutions of the original problems. We give sufficient conditions for the convergence of sequences of approximate solutions under the assumptions that the right-hand sides satisfy the nonlinear estimates of the Perron type with respect to the functional argument. In proof of the convergence of difference methods we apply theorems on difference-functional impulsive inequalities.     

COMPARISON CRITERIA OF POSITIVESOLUTIONS FOR A NEUTRAL DIFFERENCEEQUATION WITH POSITIVE AND NEGATIVE COEFFICIENTS

1.IntroductionInthispaper,weareconcernedwithaclassofneutraltypeflorenceequationswithpositiveandnegativecoefficielltsoftheformwhere',TandaarepositiveintegerssuchthatT2a){r'}:,isarealsequence3{p'}:,and{qn}Zoarenonnegativesequences.Similarequationshaver...     

Some Mixed Problems for Semilinear Parabolic type Equation

In this paper, some mixed problem with third type boundary value for a semilinear parabolic equation is investigated. Here the solvability theorems for considered problem and the uniqueness theorem for a model case of the problem are showed.     

Existence results to a nonlinear p(k)-Laplacian difference equation

In the present paper, by using variational method, the existence of non-trivial solutions to an anisotropic discrete non-linear problem involving p(k)-Laplacian operator with Dirichlet boundary condition is investigated. The main technical tools applied here are the two local minimum theorems for differentiable functionals given by Bonanno.     

Existence of almost periodic solutions for neutral delay difference systems

In this paper, the existence of almost periodic solutions is studied via the Lyapunov function. Razumikhin type theorems are established on the existence, uniqueness and uniformly asymptotic stability of almost periodic solutions. Two examples are given to explain our results.      

二阶差分方程的奇性边值问题

主要采用上下解方法,研究了一类带有奇性的二阶差分方程的两点边值问题,给出了一系列正解的存在条件.     

The first eigenvalue of Finsler p-Laplacian

The eigenvalues and eigenfunctions of p-Laplacian on Finsler manifolds are defined to be critical values and critical points of its canonical energy functional. Based on it, we generalize some eigenvalue comparison theorems of p-Laplacian on Riemannian manifolds, such as Lichnerowicz type estimate, Obata type theorem and Mckean type theorem, to the Finsler setting. Not only that, the Lichnerowicz type estimate we obtained is even better than the corresponding one in Riemannian geometry.     

Positivity of Quadratic Functionals on Time Scales: Necessity

In this work we establish that disconjugacy of a linear Hamiltonian system on time scales is a necessary condition for the positivity of the corresponding quadratic functional. We employ a certain minimal normality (controllability) assumption. Hence, the open problems stated by the author in [17], [18] are solved with the result that positivity of the quadratic functional is equivalent to disconjugacy of the Hamiltonian system on the interval under consideration. The general approach on time scales 𝕋 involves, as special cases, the well–known continuous case for 𝕋 = ℝ and recently developed discrete one for 𝕋 = ℤ so that they are unified. As applications, Sturmian type separation and comparison theorems on time scales are also provided.     

On properties of difference polynomials

We study the value distribution of difference polynomials of meromorphic functions, and extend classical theorems of Tumura-Clunie type to difference polynomials. We also consider the value distribution of f (z)f (z + c).     

Blow-up rates for higher-order semilinear parabolic equations and systems and some Fujita-type theorems

In this paper, we derive blow-up rates for higher-order semilinear parabolic equations and systems. Our proof is by contradiction and uses a scaling argument. This procedure reduces the problems of blow-up rate to Fujita-type theorems. In addition, we also give some new Fujita-type theorems for higher-order semilinear parabolic equations and systems with the time variable on R. These results are not restricted to positive solutions.     

Differentiable difference approximations for nonlinear initial-value problems.I

This paper deals with the approximation of nonlinear initial-value problems by difference methiods. in the Present part I The basic definitions and concepts are presented and equivalence theorems for stability and continuous convergenc are proved. Here, The differentiability condition (d) and the boundedness condition (Bp) are of fundamental siginificance. the latter is one of the equivalent characterizations of stability. The equivalence theorems for stability and continuous convergence include characterizations by means of locally uniform two-sided Lipschitz conditions and tow-sided discertization error estimates. At the end of part I a generalized of the concept of stable convergence of Dahlquist [2] and Torng [16] is proved to series of equivalent conditions convergence. in part II the above results will yields a series of equivalent conditions for the concepts of weak stability and conditions convergence of certain order. Moreover, further convergence concepts for semi-homogeneous methods will be studied, and hyperbolic and parawbolic example will be treated     

Ⅱ型循环拟差集

本文得到了Ⅱ型循环拟差集的一个基本性质和两个重要的不存在性定理。     

Stability of difference schemes for two-dimensional parabolic equations with non-local boundary conditions

The stability of difference schemes for one-dimensional and two-dimensional parabolic equations, subject to non-local (Bitsadze-Samarskii type) boundary conditions is dealt with. To analyze the stability of difference schemes, the structure of the spectrum of the matrix that defines the linear system of difference equations for a respective stationary problem is studied. Depending on the values of parameters in non-local conditions, this matrix can have one zero, one negative or complex eigenvalues. The stepwise stability is proved and the domain of stability of difference schemes is found.     

A difference scheme for the numerical solution of an advection equation with aftereffect

We propose a family of grid methods for the numerical solution of an advection equation with a time delay in a general form. The methods are based on the idea of separating the current state and the prehistory function. We prove the convergence of the second-order method coordinatewise and do that of the first-order with respect to time. The proof is based on techniques applied for proving analogous theorems for functional differential equations and on the general theory of difference schemes. We illustrate the obtained results with a test example.     

Implicit difference methods for evolution functional differential equations

A general theory of implicit difference schemes for nonlinear functional differential equations with initial boundary conditions is presented. A theorem on error estimates of approximate solutions for implicit functional difference equations of the Volterra type with an unknown function of several variables is given. This general result is employed to investigate the stability of implicit difference schemes generated by first-order partial differential functional equations and by parabolic problems. A comparison technique with nonlinear estimates of the Perron type for given functions with respect to the functional variable is used.     

Existence and multiplicity results for periodic solutions of nonlinear difference equations

We use Brouwer degree to prove existence and multiplicity results for the periodic solutions of some nonlinear second-order and first-order difference equations. We obtain, in particular upper and lower solutions theorems, Ambrosetti–Prodi type results and sharp existence conditions for nonlinearities which are bounded from below or above.     

Global positive periodic solutions of periodic n-species competition systems

In this paper, an easily verifiable necessary and sufficient condition for the existence of positive periodic solutions of generalized n-species Lotka-Volterra type and Gilpin-Ayala type competition systems is obtained. It improves a series of the well-known sufficiency theorems in the literature about the problems mentioned above. The method is based on a well-known fixed point theorem in a cone of Banach space. This approach can be applied to more general competition systems.