Linear functional differential equations of neutral type asymptotically autonomous

Summary It is studied the relationship between the solutions of the linear functional differential equations(1) (d/dx) D(x_t)=L(x_t) and its perturbed equation(2) [(d/dx) D(x_t)−G(t, x_t)]= =L(x_t)+F(t, x_t) and is proved, under certain hypotheses which will be precised bellow that, if μ is a simple characteristic root of(1), then there exist a σ > 0 and a non zero vector a such that system(2) has a solution satisfying where δ(t)=αd{F(t, ϕ_μ)+μG(t, ϕ_μ)+F(t, X₀G(t, ϕ_μ))}, ϕ_μ(θ)=c·exp (μθ), −r⩾θ⩾0 and α, d, X₀ are given constants. Entrata in Redazione il 5 gennaio 1972.     

Periodic solutions of asymptotically linear autonomous Newtonian systems with resonance

In this paper, we study the existence, continuation and bifurcation from infinity of2π$2\pi$-periodic solutions of autonomous Newtonian systems. We underline that the resonant case is considered. To prove the results, we apply the degree for S¹$S^1$-equivariant gradient maps defined by Rybicki (1994) in [15] and the angle condition introduced by Bartsch and Li (1997) in [16].     

On exterior Neumann problems with an asymptotically linear nonlinearity

In this paper, we study exterior Neumann problems with an asymptotically linear nonlinearity. We establish the existence of ground state solutions. Furthermore when the domain is a complement of a ball, we prove the ground state solutions are not radially symmetric. We also give asymptotic profiles of ground state solutions.     

Attractor of Smale - Williams type in an autonomous distributed system

We consider an autonomous system of partial differential equations for a one-dimensional distributed medium with periodic boundary conditions. Dynamics in time consists of alternating birth and death of patterns with spatial phases transformed from one stage of activity to another by the doubly expanding circle map. So, the attractor in the Poincaré section is uniformly hyperbolic, a kind of Smale - Williams solenoid. Finite-dimensional models are derived as ordinary differential equations for amplitudes of spatial Fourier modes (the 5D and 7D models). Correspondence of the reduced models to the original system is demonstrated numerically. Computational verification of the hyperbolicity criterion is performed for the reduced models: the distribution of angles of intersection for stable and unstable manifolds on the attractor is separated from zero, i.e., the touches are excluded. The example considered gives a partial justification for the old hopes that the chaotic behavior of autonomous distributed systems may be associated with uniformly hyperbolic attractors.     

Linear system identification via an asymptotically stable observer

This paper presents a formulation for identification of linear multivariable systems from single or multiple sets of input-output data. The system input-output relationship is expressed in terms of an observer, which is made asymptotically stable by an embedded eigenvalue assignment procedure. The prescribed eigenvalues for the observer may be real, complex, mixed real and complex, or zero corresponding to a deadbeat observer. In this formulation, the Markov parameters of the observer are first identified from input-output data. The Markov parameters of the actual system are then recovered from those of the observer and used to realize a state space model of the system. The basic mathematical formulation is derived, and numerical examples are presented to illustrate the proposed method.     

Construction of an asymptotically periodic solution to one nonstationary system with delay

In this paper we consider an ensemble of two subsystems of linear differential equations with constant delay. One of the subsystems contains an exponential multiplier in its right-hand side. We construct an asymptotically periodic solution of this system.     

Strong regularizing effect of a gradient term in the heat equation with the Hardy potential

We deal with the following parabolic problem,

     

Stability of an autonomous dynamic system with fast Markov switching

For an autonomous dynamic system with a fast Markov switching, sufficient conditions for asymptotic stability in the presence of a Lyapunov function which assures stability of a stationary averaged system are established.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 9, pp. 1176–1181, September, 1991.     

On an elliptic equation of Kirchhoff-type with a potential asymptotically linear at infinity

This paper examines the existence of positive solutions for a boundary value problem of Kirchhoff-type involving a positive potential function which is asymptotically linear at infinity.     

On an asymptotically more efficient estimation of the single-index model

In this note, we revisit the single-index model with heteroscedastic error, and recommend an estimating equation method in terms of transferring restricted least squares to unrestricted least squares: the estimator of the index parameter is asymptotically more efficient than existing estimators in the literature in the sense that it is of a smaller limiting variance.     

On an elliptic attractor in an asymptotically symmetric unbounded domain in RFormula

We study the positive solutions of a semilinear elliptic problemin an asymptotically symmetric unbounded domain ₊ in ⁴. Theexistence of the global attractor for the trajectory dynamicalsystem associated with this problem is proved. Based on therecent development of the De Giorgi conjecture, the symmetrizationand stabilization properties of positive solutions as |x| arealso established in the four-dimensional case.     

二阶渐近周期奇异哈密顿系统同宿轨道

运用集中紧性方法和Ekeland变分原理研究R^2中二阶渐近周期奇异Hamilton系统ue (1 g(t))V‘u(t,u)=0的极小问题,并证明该系统具有两条非平凡同宿轨道。     

On Liouville type theorems for fully nonlinear elliptic equations with gradient term

In this paper, we prove a Hadamard property and Liouville type theorems for viscosity solutions of fully nonlinear elliptic partial differential equations with a gradient term, both in the whole space and in an exterior domain.     

Finitely smooth normal form of an autonomous system with two pure imaginary roots

We consider the problem of finitely smooth normalization of a system of ordinary differential equations whose linear part has two eigenvalues, while the other eigenvalues lie outside the imaginary axis.     

On a viscous Hamilton-Jacobi equation with an unbounded potential term

We present comparison, uniqueness and existence results for unbounded solutions of a viscous Hamilton-Jacobi or eikonal equation. The equation includes an unbounded potential term V(x) subject to a quadratic upper bound. The results are obtained through a tailor-made change of variables in combination with the Hopf-Cole transformation. An integral representation formula for the solution of the Cauchy problem is derived in the case where V(x)=ω²|x|²/2.     

On the Poincaré theorem with asymptotically periodic coefficients

We consider the case where the Poincaré theorem for difference equations with asymptotically constant coefficients is generalized to systems of difference equations with asymptotically periodic coefficients. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 9, pp. 1262–1267, September, 1998.