Approximately order zero maps between C*-algebras

Abstract

We investigate linear operators between C$^\ast$-algebras which approximately preserve involution and orthogonality, the latter meaning that for some $\varepsilon>0$ we have $\|\phi(x)\phi(y)\|\leq\varepsilon\|x\|\|y\|$ for all positive $x,y$ with $xy=0$. We establish some structural properties of such maps concerning approximate Jordan-like equations and almost commutation relations. In some situations (e.g. when the codomain is finite-dimensional), we show that $\phi$ can be approximated by an approximate Jordan $^\ast$-homomorphism, with both errors depending only on $\|\phi\|$ and $\varepsilon$.