Almost orthogonally additive functions

Tomasz Kochanek, Wirginia Wyrobek-Kochanek

If a function $f$, acting on a Euclidean space ${\mathbb{R}}^n$, is "almost" orthogonally additive in the sense that $f(x+y)=f(x)+f(y)$ for all $(x,y)\in \perp \setminus Z$, where $Z$ i…