Approximations of Lipschitz maps with maximal derivatives on Banach spaces

TL;DR

This paper investigates how Lipschitz maps with maximal derivatives can be approximated in Banach spaces, linking these approximations to the Radon-Nikodým property and extending previous results on maximal affine functions.

Contribution

It characterizes the Radon-Nikodým property via Lipschitz map approximations and extends approximation results for Lipschitz functionals on the real line.

Findings

Characterization of Radon-Nikodým property through Lipschitz map approximations.

Local approximation of Lipschitz functionals by maximal affine functions.

Limitations of uniform approximation for maximal affine functions.

Abstract

We study two types of approximations of Lipschitz maps with derivatives of maximal slopes on Banach spaces. First, we characterize the Radon-Nikod\'ym property in terms of strongly norm attaining Lipschitz maps and maximal derivative attaining Lipschitz maps, which complements the characterization presented in \cite{CCM}. It is shown in particular that if every Lipschitz map can be approximated by those that either strongly attain their norm or attain their maximal derivative for every renorming of the range space, then the range space must have the Radon-Nikod\'ym property. Next, we prove that every Lipschitz functional defined on the real line can be locally approximated by maximal affine functions, while such an approximation cannot be guaranteed in the context of uniform approximation. This extends the previous work in \cite{BJLPS} in view of maximal affine functions.