Quadratic-quartic functional equations in RN-spaces.
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Gordji, M.Eshaghi, Savadkouhi, M.Bavand, Park, Choonkil (2009)
Journal of Inequalities and Applications [electronic only]
Félix Cabello Sánchez (2003)
Fundamenta Mathematicae
We study the stability of homomorphisms between topological (abelian) groups. Inspired by the "singular" case in the stability of Cauchy's equation and the technique of quasi-linear maps we introduce quasi-homomorphisms between topological groups, that is, maps ω: 𝒢 → ℋ such that ω(0) = 0 and ω(x+y) - ω(x) - ω(y) → 0 (in ℋ) as x,y → 0 in 𝒢. The basic question here is whether ω is approximable by a true homomorphism a in the sense that ω(x)-a(x) → 0 in ℋ as x →...
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