## On a ρ-orthogonality

ρ-orthogonality is one among many possible definitions of orthogonality in general normed spaces, related to the “derivatives” of the norm.

The talk is based on the article (of the same title) by Jacek Chmieliński and Paweł Wójcik (Aequat. Math. 2010). Apart from basic properties of the introduced notion, the class of maping preserving ρ-orthogonality will be considered.