Monotone and numerical-analytic methods for differential equations

The method of lower and upper solutions combined with monotone iterative techniques is used for ordinary differential equations with integral boundary conditions showing the existence of extremal solutions. Some existence results are also formulated using the numerical-analytic method. Sufficient conditions for existence are given.     

Penalty approximation method for a class of elliptic variational inequality problems

In this paper, two existence results of solutions for a class of elliptic variational inequalities are obtained by considering the approximations of the solutions to a class of penalized differential equations.     

Existence and approximation of solutions for first-order discontinuous difference equations with nonlinear global conditions in the presence of lower and upper solutions

This paper is devoted to the study of the existence of solutions of first-order difference equations verifying nonlinear conditions that involve the global behavior of the solution. We prove that the existence of lower and upper solutions warrants the existence of such solutions lying in the sector formed by the mentioned functions. We also can prove that some classical results for differential equations are not true in general for this case.     

Existence of monotone and slow solutions for differential inclusions

The existence of slow and monotone solutions with respect to a continuous pre-order is proved for differential inclusions defined on a closed convex subset of R⁴. First we examine the ‘projected system’, and prove that it is equivalent to a differential variational inequality. We then establish the existence of monotone trajectories. Subsequently, we prove the existence of slow monotone solutions for a class of differential inclusions, satisfying a Nagumo-type condition. Finally we prove a convergence result.     

Boundary value problems for a class of impulsive functional equations

This paper is related to the existence and approximation of solutions for impulsive functional differential equations with periodic boundary conditions. We study the existence and approximation of extremal solutions to different types of functional differential equations with impulses at fixed times, by the use of the monotone method. Some of the options included in this formulation are differential equations with maximum and integro-differential equations. In this paper, we also prove that the Lipschitzian character of the function which introduces the functional dependence in a differential equation is not a necessary condition for the development of the monotone iterative technique to obtain a solution and to approximate the extremal solutions to the equation in a given functional interval. The corresponding results are established for the impulsive case. The general formulation includes several types of functional dependence (delay equations, equations with maxima, integro-differential equations). Finally, we consider the case of functional dependence which is given by nonincreasing and bounded functions.     

Difference equations in Banach spaces

Difference equations which discretely approximate boundary value problems for second-order ordinary differential equations are analysed. It is well known that the existence of solutions to the continuous problem does not necessarily imply existence of solutions to the discrete problem and, even if solutions to the discrete problem are guaranteed, they may be unrelated and inapplicable to the continuous problem.Analogues to theorems for the continuous problem regarding a priori bounds and existence of solutions are formulated for the discrete problem. Solutions to the discrete problem are shown to converge to solutions of the continuous problem in an aggregate sense.An example which arises in the study of the finite deflections of an elastic string under a transverse load is investigated. The earlier results are applied to show the existence of a solution; the sufficient estimates on the step size are presented.     

Three-point boundary value problems for second-order discrete equations

We formulate existence results for solutions to discrete equations which approximate three-point boundary value problems for second-order ordinary differential equations.     

Existence results for impulsive differential inclusions with nonlocal conditions

In this paper, we shall establish sufficient conditions for the existence of mild solutions for nonlocal impulsive differential inclusions. On the basis of the fixed point theorems for multivalued maps and the technique of approximate solutions, new results are obtained. Examples are also provided to illustrate our results.     

Stability and existence of periodic solutions in inertial BAM neural networks with time delay

In this paper, the global exponential stability and existence of periodic solutions for inertial BAM neural networks are investigated. The system is transformed to first-order differential equation with chosen variable substitution. Then, some new sufficient conditions that ensure the existence and exponential stability of periodic solutions for the system are obtained by constructing suitable Lyapunov function, using Weierstrass criteria and boundedness of solutions. Finally, an example is given to illustrate the effectiveness of the results.     

Nontrivial solutions for a nonlinear multi-point boundary value problem of fractional order

We investigate the existence of nontrivial solutions for a multi-point boundary value problem for fractional differential equations. Under certain growth conditions on the nonlinearity, several sufficient conditions for the existence of nontrivial solution are obtained by using Leray–Schauder nonlinear alternative. As an application, some examples to illustrate our results are given.     

Optimal existence conditions for second order periodic solutions of delay differential equations with upper and lower solutions in the reverse order

In this paper we show that the monotone iterative technique provides two monotone sequences that converge uniformly to extremal (periodic) solutions of second order delay differential equations without assuming properties of monotonicity in the nonlinear part. Moreover, we obtain optimal existence conditions with upper and lower solutions in the reverse order. Our results are new even for ordinary differential equations.     

Existence results for the three-point impulsive boundary value problem involving fractional differential equations

In this paper, we consider the existence of solutions for a class of three-point boundary value problems involving nonlinear impulsive fractional differential equations. By use of Banach’s fixed point theorem and Schauder’s fixed point theorem, some existence results are obtained.     

Analytic study on linear systems of fractional differential equations

An analytic study on linear systems of fractional differential equations with constant coefficients is presented. We briefly describe the issues of existence, uniqueness and stability of the solutions for two classes of linear fractional differential systems. This paper deals with systems of differential equations of fractional order, where the orders are equal to real number or rational numbers between zero and one. Exact solutions for initial value problems of linear fractional differential systems are analytically derived. Existence and uniqueness results are proved for two classes. The presented results are illustrated by analyzing some examples to demonstrate the effectiveness of the presented analytical approaches.     

Variational methods to the second-order impulsive differential equation with Dirichlet boundary value problem

In this paper, we study the existence of solutions for a class of second-order impulsive differential equation. By using the critical point theorem of Y. Jabri and an even functional theorem, we give some new criteria to guarantee that the impulsive differential equation has at least one solution, infinitely many solutions under the assumption that a nonlinear term satisfies sublinear, superlinear, asymptotically linear, respectively. Some recent results are extended and conditions of assumptions are simplified. Finally, some examples are presented to illustrate our main results.     

Perfect bases for differential equations

We present a method for the construction of solutions of certain systems of partial differential equations with polynomial and power series coefficients. For this purpose we introduce the concept of perfect differential operators. Within this framework we formulate division theorems for polynomials and power series. They in turn yield existence theorems for solutions of systems of linear partial differential equations and algorithms to explicitly construct solutions.     

On global existence of solutions to coupled matrix Riccatiequations in closed-loop Nash games

Presents comparison and global existence results for solutions of coupled matrix Riccati differential equations appearing in closed loop Nash games and in mixed H₂/H_∞-type problems. Convergence of solutions is established for the diagonal case, solutions of the corresponding algebraic equations are discussed using numerical examples     

Existence of solutions for second-order perturbed nonconvex sweeping process

We prove a theorem on the existence solutions for a second-order differential inclusion governed by a class of nonconvex sweeping process. Our result improves and generalizes many results from the literature of sweeping process.     

Solutions to the Cauchy problem for differential equations in Banach spaces with fractional order

In this paper, we use the monotone iterative technique combined with cone theory to investigate the existence of solutions to the Cauchy problem for Caputo fractional differential equations in Banach spaces. New existence theorems are obtained for the case of a cone P being normal and fully regular respectively. Moreover, two examples are given to illustrate the abstract results.     

Theory of fractional hybrid differential equations

In this paper, we develop the theory of fractional hybrid differential equations involving Riemann-Liouville differential operators of order 0<q<1. An existence theorem for fractional hybrid differential equations is proved under mixed Lipschitz and Carathéodory conditions. Some fundamental fractional differential inequalities are also established which are utilized to prove the existence of extremal solutions. Necessary tools are considered and the comparison principle is proved which will be useful for further study of qualitative behavior of solutions.     

Uncertain impulsive differential systems of fractional order: almost periodic solutions

In this paper, we investigate the existence and stability of almost periodic solutions of impulsive fractional-order differential systems with uncertain parameters. The impulses are realised at fixed moments of time. For the first time, we determine the impact of the uncertainties on the qualitative behaviour of such systems. The main criteria for the existence of almost periodic solutions are proved by employing the fractional Lyapunov method. The global perfect robust uniform-asymptotic stability of such solutions is also considered. We apply our results to uncertain impulsive neural network systems of fractional order.