D. Popa

activity

20102026

collaborators

5 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…

math.FA2015

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

Soon-Mo Jung, Dorian Popa, Michael Th. Rassias

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

math.FA2010

On the stability of the first order linear recurrence in topological vector spaces

Mohammad Sal Moslehian, Dorian Popa

Suppose that $X$ is a sequentially complete Hausdorff locally convex space over a scalar field $K$ , $V$ is a bounded subset of $X$ , $(a_{n})_{n \geq 0}$ is…