Positive periodic solutions of nonautonomous functional differential systems

Considered is the periodic functional differential system with a parameter, x^′(t)=A(t,x(t))x(t)+λf(t,xt). Using the eigenvalue problems of completely continuous operators, we establish some criteria on the existence of positive periodic solutions. Moreover, we apply the results to a couple of population models and obtain sufficient conditions for the existence of positive periodic solutions, which are compared with existing ones.     

Multiple periodic solutions for nonautonomous Hamiltonian systems

In this paper, by the use of minimax method, we obtain some existence and multiplicity theorems for periodic solutions of nonautonomous Hamiltonian systems with bounded nonlinearity of the type:¶ J [(x)\dot] + ?H(t, x) + e(t) = 0. J \dot x + \nabla H(t, x) + e(t) = 0.     

On isolated periodic solutions of differential systems

Summary The concept of an isolated periodic solution of a periodic differential system is defined and it is proved that if the number 1 is not a characteristic multiplier of the variational system corresponding to the given periodic solution then this solution is isolated. The concept of a periodic solution with isolated path of an autonomous system is defined and it is proved that if the number 1 is a simple characteristic multiplier of the corresponding variational system then the periodic solution has an isolated path. An example is given showing that the conditions above are not necessary. Entrata in Redazione l’8 giugno 1974.     

On the dynamics of nonautonomous periodic general dynamical systems and differential inclusions

We establish the existence and stability results for periodic nonautonomous uniform forward attractors of periodic general dynamical systems (set-valued dynamical systems). We also investigate the dynamical behavior of nonautonomous periodic differential inclusion x^′(t)∈f(t,x(t)) on R^m with only upper semi-continuous right-hand side by applying the abstract results. Firstly, we show that if the system has a compact uniformly attracting set, then it has a periodic nonautonomous uniform forward attractor A. Secondly, we prove that A is robust with respect to both internal and external perturbations. Finally, we apply the robustness result to discuss the effects of small time delays to asymptotic stability of the system.     

Reflecting function and solutions of two-point boundary value problems for nonautonomous two-dimensional differential systems

For a second-order nonlinear system whose linear approximation is the harmonic oscillator system, we obtain necessary and sufficient conditions for the coincidence of its reflecting function with the reflecting function of the linear approximation system.     

A note on periodic solutions of nonautonomous second-order systems

A multiplicity theorem is obtained for periodic solutions of nonautonomous second-order systems with partially periodic potentials by the minimax methods.

     

On generalized-periodic solutions of nonautonomous differential inclusions

We introduce the notion of a generalized-periodic solution of a classical nonautonomous differential inclusion with periodic right-hand side. We show that the existence of a bounded solution implies the existence of a generalized-periodic solution, and vice versa.     

On periodic solutions of nonlinear second order differential systems

The paper deals with the second order differential systems with periodic boundary conditions. In the first part of the paper four different methods are employed to find the unique solution of the linear systems. One of the methods is a shooting type which converts the periodic boundary value problem into its equivalent initial value problem. In the second part of the paper several sufficient conditions are provided for the existence and uniqueness for the nonlinear systems. The technique developed for the linear systems to convert into its equivalent initial value problem is used in an iterative way for the nonlinear systems. It is shown that the iterations converge quadratically.     

Nontrivial periodic solutions of a nonautonomous system of second-order differential equations

We prove theorem, in which basic conditions for the existence of nontrivial periodic solutions are formulated in terms of the properties of the elements of the matrix of a linear approximation to a system. Ryazan Pedagogical Institute, Ryazan. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 6, pp. 754–759, June, 1994.     

Existence of nontrivial periodic solutions of certain nonautonomous ordinary differential equations

Degree theory is used to establish sufficient conditions for the existence of a non-trivial periodic solution of the vector differential equation f(D)x + BMg(D)x = 0, which generalises the feedback control equation. These conditions require that the matrix M should satisfy two elliptic ball criteria, one of which is relevant near the origin of the phase space and the other near the point at infinity.     

非自治时滞微分方程正周期解的存在性

应用Krasnoselskii锥映射不动点定理，研究了具一般时滞非线性非自治Logistic方程的ω-周期解的存在性，获得了存在正周期解的充分条件．     

On the qualitative behavior of periodic solutions of differential systems

This article deals with the reflective function of differential systems. The obtained results are applied to studying the existence and stability of the periodic solutions of some linear and nonlinear periodic differential systems.     

Algorithm for the numerical proof of the existence of periodic trajectories in two-dimensional nonautonomous systems of ordinary differential equations

We suggest an algorithm that permits one to prove the existence of limit periodic trajectories (cycles) in two-dimensional nonautonomous dissipative systems with periodic coefficients with the use of computational methods alone. We prove a fixed point theorem for two-dimensional mappings and describe methods of its application to two-dimensional nonautonomous systems with the use of the Poincaré mapping and interval arithmetics.     

Analysis of nonautonomous systems of ordinary differential equations with exponentially periodic matrix

We investigate a class of nonautonomous systems of ordinary differential equations whose matrix can be characterized as exponentially periodic. We develop the algorithm of spectral analysis of these systems. By this algorithm we prove reducibility theorems. The proposed algorithm is based on the splitting method that allows to reduce considered systems to simpler ones with quasidiagonal matrix, and formulate constructive conditions of solutions stability.