There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

In this paper, we study the stability of functional equations that has its origins with S. M. Ulam, who posed the fundamental problem 60 years ago and with D. H. Hyers, who gave the first significant partial solution in 1941. In particular, during the last two decades, the notion of stability of functional equations has evolved into an area of continuing research from both pure and applied viewpoints. Both classical results and current research are presented in a unified and self-contained fashion. In addition, related problems are investigated. Some of the applications deal with nonlinear equations in Banach spaces and complementarity theory.

On the Stability of Functional Equations and a Problem of Ulam

On the Stability of Functional Equations in Banach Spaces

Introduction 1. Packaging and covering densities 2. The existence of reasonably dense packings 3. The existence of reasonably economical coverings 4. The existence of reasonably dense lattice packings 5. The existence of reasonably economical lattice coverings 6. Packings of simplices cannot be very dense 8. Coverings with spheres cannot be very economical Bibliography Index.

Packing and Covering. By C. A. Rogers. Pp. viii, 111. 30s. 1964. (Cambridge)

Hyers-Ulam stability of linear differential equations of first order

On the Hyers–Ulam Stability of the Functional Equations That Have the Quadratic Property☆

Hyers-Ulam stability of linear differential equations of first order, III

Hyers–Ulam stability of a system of first order linear differential equations with constant coefficients☆

We will apply the fixed point method for proving the Hyers-Ulam-Rassias stability of a Volterra integral equation of the second kind.

https://link.springer.com/content/pdf/10.1155%2F2007%2F57064.pdf

Soon-Mo Jung

Papers

Hyers-Ulam stability of linear differential equations of first order

On the Hyers–Ulam Stability of the Functional Equations That Have the Quadratic Property☆

Hyers-Ulam stability of linear differential equations of first order, III

Hyers–Ulam stability of a system of first order linear differential equations with constant coefficients☆

A Fixed Point Approach to the Stability of a Volterra Integral Equation