Displaying similar documents to “A Hahn-Banach type generalization of the Hyers-Ulam theorem.”

On subadditive functions and ψ-additive mappings

Janusz Matkowski (2003)

Open Mathematics


In [4], assuming among others subadditivity and submultiplicavity of a function ψ: [0, ∞)→[0, ∞), the authors proved a Hyers-Ulam type stability theorem for “ψ-additive” mappings of a normed space into a normed space. In this note we show that the assumed conditions of the function ψ imply that ψ=0 and, consequently, every “ψ-additive” mapping must be additive