Hyers-Ulam stability of a general linear partial differential equation

Aequationes mathematicae - In this paper we will study Hyers-Ulam stability for a general linear partial differential equation of first order in a Banach space.     

On the Hyers-Ulam stability of the linear differential equation

We obtain some results on generalized Hyers-Ulam stability of the linear differential equation in a Banach space. As a consequence we improve some known estimates of the difference between the perturbed and the exact solutions.     

Hyperstability of general linear functional equation

Our purpose is to investigate criteria for hyperstability of linear type functional equations. We prove that a function satisfying the equation approximately in some sense, must be a solution of it. We give some conditions on coefficients of the functional equation and a control function which guarantee hyperstability. Moreover, we show how our outcomes may be used to check whether the particular functional equation is hyperstable. Some relevant examples of applications are presented.     

Remark on hyperstability of the general linear equation

We present a result concerning the hyperstability of the general linear equation. Namely, we show that a function satisfying the equation approximately must be actually a solution to it.     

On the uniform asymptotic stability for a linear integro-differential equation of Volterra type

In this paper, we give a necessary and sufficient condition on the uniform asymptotic stability of the zero solution of a linear integro-differential equation of Volterra type where the ordinary part is ax(t). We put emphasis on the case a>0. The proofs of our results are carried out by using the root analysis of the characteristic equation. In Section 5 we give some conjectures.     

On the stability of the linear differential equation of higher order with constant coefficients

We obtain a result on stability of the linear differential equation of higher order with constant coefficients in Aoki-Rassias sense. As a consequence we obtain the Hyers-Ulam stability of the above mentioned equation. A connection with dynamical sytems perturbation is established.     

On singular ordinary linear differential operators related to Orr-Sommerfeld stability equation

A usable, not technically complicated theory unlike that of Wasow of linear, singular, even order differential operators with general boundary conditions is proposed and the behaviour of eigenvalues and eigenfunctions is discussed in the limit as ε → 0, ε > 0. Completeness of the eigenvalue spectrum when the operator is formally self-adjoint is discussed and formal solutions are constructed and finally justification of the formal approximations is shown by proving the existence of actual solutions of the differential equation approximated by formal solutions. Also, modifications necessary for the consideration of the critical point are suggested. This theory is unlike that of Reid since it provides rigorous justification of the approximations and moreover, this theory is applicable to a large class of physical problems rewritten in such a way that they contain a small parameter.     

The hyperstability of general linear equation via that of Cauchy equation

Aequationes mathematicae - In this paper, we show that the hyperstability of the general linear equation recently proved by Piszczek (Aequationes Math 88:163–168, 2014) is a direct...     

Locally compact set-valued solutions for the general linear equation

Summary. We give a representation for the set-valued solutions, with closed convex and locally compact values, of a general linear equation as a sum of an additive mapping and a constant set.     

A general functional equation and its stability

Suppose that and are vector spaces over or and are scalar such that whenever We prove that if for and

then each is a ``generalized' polynomial map of ``degree' at most

In case and we show that if some is bounded on a set of positive inner Lebesgue measure, then it is a genuine polynomial function.

Our main aim is to establish the stability of (in the sense of Ulam) in case is a Banach space.

We also solve a distributional analogue of and prove a mean value theorem concerning harmonic functions in two real variables.

     

On the stability of the transport equation

We consider boundary value problems associated with the equation T=–A in a Hilbert Space, where T and A are bounded, self adjoint, injective, and A has a bounded inverse. We discuss the stability of the solution when A is perturbed by a self adjoint operator.     

On the stability of the linear functional equation in a single variable on complete metric groups

In this paper we obtain a result on Hyers–Ulam stability of the linear functional equation in a single variable $f(\varphi (x)) = g(x) \cdot f(x)$ on a complete metric group.