D. Popa

activity

20202026

collaborators

3 papers

math.AP2026

An integral formula for the inhomogeneous Jordan--von Neumann equation

Alexandra Paicu, Dorian Popa, Mircea Dan Rus

We study the inhomogeneous form of the Jordan--von Neumann quadratic functional equation, in which the right-hand side is a prescribed function $g$ of two real variables. We prove…

math.CA2021

On the best Ulam constant of the linear differential operator with constant coefficients

Alina-Ramona Baias, Dorian Popa

The linear differential operator with constant coefficients $D (y) = y^{(n)} + a_{1} y^{(n - 1)} + \dots + a_{n} y, y \in C^{n} (R, X)$ acting in a Banach space $X$ is Ul…

math.FA2020

On the best Ulam constant of a higher order linear difference equation

Alina Ramona Baias, Dorian Popa

In a Banach space $X$ the linear difference equation with constant coefficients $x_{n + p} = a_{1} x_{n + p - 1} + \dots + a_{p} x_{n},$ is Ulam stable if and only if the roots $r_{k},$ $1\leq k\l…