Positiveness conditions for the Cauchy function for differential equations with distributed delay

We obtain unimprovable sufficient conditions for the positivity of the Cauchy function for differential equation with distributed delay. Based on these conditions, we study some asymptotic properties of solutions of the Hutchinson-Wright equation, the Lasota-Wazevska equation, and the Nicholson equation.     

On the solution of the Gellerstedt problem for the Lavrent’ev-Bitsadze equation

We study the solvability of the Gellerstedt problem for the Lavrent??ev-Bitsadze equation under an inhomogeneous boundary condition on the half-circle of the ellipticity domain of the equation, homogeneous boundary conditions on external, internal, and parallel side characteristics of the hyperbolicity domain of the equation, and the transmission conditions on the type change line of the equation.     

The continuous dependence of solutions to Volterra equations with locally contracting operators on parameters

For a Volterra equation in a function space we obtain conditions for the unique existence of a global or maximally extended solution and its continuous dependence on equation parameters. Based on these results, we state conditions for the solvability of the Cauchy problem for a differential equation with delay and the continuous dependence of solutions on the right-hand side of the equation, on the delay, on the initial condition, and the history.     

具正负系数的二阶中立型时滞差分方程的振动和非振动准则

研究了一类具有正负系数的二阶非线性中立型时滞差分方程的振动性,利用Banach空间的不动点原理,结合Riccati变换,获得了该类方程存在非振动解的一些新的准则,并同时得到了该类方程振动的判别准则,这些准则改善了对方程的条件限制,所得结论推广并改进了现有文献中的一系列结果.     

一类非线性算子方程的正解问题

研究算子方程X^s+A^*X^-tA=Q的正算子解的存在性问题,通过构造有效的迭代序列,给出了算子方程X^s+A^*X^-tA=Q有正算子解的一些充分条件和必要条件,同时给出了该方程有极大解和唯一解的条件.     

Conditions for stabilization of solutions to the first boundary value problem for parabolic equations

We study the stabilization to zero of a solution to the first boundary value problem for a parabolic equation. We obtain necessary and sufficient stabilization conditions in the case of the heat equation and sufficient conditions in the case of a parabolic equation with variable coefficients. Bibliography: 14 titles.     

What Is a Quantum Stochastic Differential Equation from the Point of View of Functional Analysis?

We prove that a quantum stochastic differential equation is the interaction representation of the Cauchy problem for the Schrödinger equation with Hamiltonian given by a certain operator restricted by a boundary condition. If the deficiency index of the boundary-value problem is trivial, then the corresponding quantum stochastic differential equation has a unique unitary solution. Therefore, by the deficiency index of a quantum stochastic differential equation we mean the deficiency index of the related symmetric boundary-value problem.In this paper, conditions sufficient for the essential self-adjointness of the symmetric boundary-value problem are obtained. These conditions are closely related to nonexplosion conditions for the pair of master Markov equations that we canonically assign to the quantum stochastic differential equation.     

Mixed Problem for an Ultraparabolic Equation in Unbounded Domain

We investigate a mixed problem for a nonlinear ultraparabolic equation in a certain domain Q unbounded in the space variables. This equation degenerates on a part of the lateral surface on which boundary conditions are given. We establish conditions for the existence and uniqueness of a solution of the mixed problem for the ultraparabolic equation; these conditions do not depend on the behavior of the solution at infinity. The problem is investigated in generalized Lebesgue spaces.     

Stability of a linear nonautonomous difference equation with bounded delays

We obtain exact sufficient stability conditions for a linear nonautonomous difference equation with several bounded delays. These conditions are written in terms of parameters of the initial equation.     

Theory of bifurcations of the Schrödinger equation

We obtain solvability conditions and a representation of solutions for a boundary value problem for a linear nonstationary Schrödinger equation in a Hilbert space as well as sufficient conditions for the bifurcation of solutions of this equation.     

Explicit stability conditions for integro-differential equations with periodic coefficients

New explicit stability conditions are derived for a linear integro-differential equation with periodic operator coefficients. The equation under consideration describes oscillations of thin-walled viscoelastic structural members driven by periodic loads. To develop stability conditions two approaches are combined. The first is based on the direct Lyapunov method of constructing stability functionals. It allows stability conditions to be derived for unbounded operator coefficients, but fails to correctly predict the critical loads for high-frequency excitations. The other approach is based on transforming the equation under consideration in such a way that an appropriate ‘differential’ part of the new equation would possess some reserve of stability. Stability conditions for the transformed equation are obtained by using a technique of integral estimates. This method provides acceptable estimates of the critical forces for periodic loads, but can be applied to equations with bounded coefficients only. Combining these two approaches, we derive explicit stability conditions which are close to the Floquet criterion when the integral term vanishes. These conditions are applied to the stability problem for a viscoelastic bar compressed by periodic forces. The effect of material and structural parameters on the critical load is studied numerically. © 1998 B. G. Teubner Stuttgart–John Wiley & Sons Ltd.     

Optimal Control Problems for Evolution Equations of Parabolic Type with Nonlinear Perturbations

In this paper, we study the optimal control problems governed by the semilinear parabolic type equation in Hilbert spaces. Under Lipschitz continuity condition of the nonlinear term, we can obtain the optimal conditions and maximal principles for a given equation, which are described by the adjoint state corresponding to the given equation without the rigorous conditions for the nonlinear term.     

Abstract Euler–Poisson–Darboux equation with nonlocal condition

We find conditions for the unique solvability of nonlocal problems for abstract differential equation of the Euler–Poisson–Darboux equation. Nonlocal conditions contain either Erdelyi–Kober operator or Riemann–Liouville fractional integration operator.     

Problem without Initial Conditions for a Class of Inverse Parabolic Operator-Differential Equations of Third Order

In a weighted Sobolev-type space, the well-posedness and unique solvability of a problem without initial conditions for a third-order operator-differential equation with an inverse parabolic principal part are established. The solvability conditions are expressed in terms of the operator coefficients of the equation. Additionally, the norms of the operators of intermediate derivatives closely related to the solvability conditions are estimated. The relation between the weight exponent and the lower boundary of the spectrum of the basic operator involved in the principal part of the equation is established. Note that the principal part of the equation has a multiple characteristic.     

关于带有三点边值的非线性分数阶积分微分方程的解的存在性和惟一性

本文考虑一个带有三点边值的非线性分数阶积分微分方程,并分别用Krasnoselskii不动点定理和Banach压缩映像原理建立了其解的存在性和惟一性的充分条件.     

Periodic problem for an evolution equation with a quadratic and a cubic nonlinearity

We study conditions for the existence of a solution of a periodic problem for a model nonlinear equation in the spatially multidimensional case and consider various types of large time asymptotics (exponential and oscillating) for such solutions. The generalized Kolmogorov-Petrovskii-Piskunov equation, the nonlinear Schrödinger equation, and some other partial differential equations are special cases of this equation. We analyze the solution smoothing phenomenon under certain conditions on the linear part of the equation and study the case of nonsmall initial data for a nonlinearity of special form. The leading asymptotic term is presented, and the remainder in the asymptotics of the solution is estimated in a spatially uniform metric.     

Nonlinear Mathieu equation and coupled resonance mechanism

The method of multiple-scales is used to determine a third-order solution for a cubic nonlinear Mathieu equation. The perturbation solutions are imposed on the so-called solvability conditions. Solvability conditions in the non-resonance case yield the standard Landau equation. Several types of a parametric Landau equation are derived in the neighborhood of five different resonance cases. These parametric Landau equations contain a parametric complex conjugate term or a parametric second-order complex conjugate term or a parametric complex conjugate term as well as a parametric second-order term. Necessary and sufficient conditions for stability are performed in each resonance case. Stability criteria correspond to each parametric Landau equation and are derived by linear perturbation. Stability criteria for the non-trivial steady-state response are discussed. The analysis leads to simultaneous resonance. Transition curves are performed in each case. Numerical calculations are made for some transition curves to illustrate the coupled resonance regions, where the induced stability tongues within the instability tongues are observed. The amplitude of the periodic coefficient of Mathieu equation plays a dual role in the stability criteria for nonlinear Mathieu equation.     

On a mixed problem with integral conditions for one-dimensional parabolic equation

We consider an initial-boundary value problem for a one-dimensional parabolic equation with nonlocal boundary conditions. These nonlocal conditions are given in terms of integrals. Based on solution of the Dirichlet problem for the parabolic equation, we constructively establish the well-posedness for the nonlocal problem.     

Tensor conditions for the existence of a common solution to the Lyapunov equation

Necessary and sufficient conditions for the existence of a common solution to the Lyapunov equation for two stable complex matrices are derived. These conditions are applied to the cases when a common weak solution to the Lyapunov equation exists. Conditions for the existence of a common solution to the Lyapunov equation for two complex 2 × 2 and two complex 3 × 3 matrices are derived.     

Adomian's method of decomposition: critical review and examples of failure

Adomian's method of decomposition is considered in application to initial-boundary value problems for the one space-dimensional spatially homogeneous heat conduction equation. It is shown that the fundamental equation of the method is well-defined only for certain restricted types of boundary conditions. Within the class of such boundary conditions, examples are given such that the fundamental equation fails to have a unique solution, and such that the sequence produced by iteration of this equation is divergent. The latter is a counterexample to a published assertion of convergence.