Some sharp Schwarz type estimates and their applications in Banach spaces

TL;DR

This paper develops improved Schwarz type estimates and applies them to derive sharp boundary lemmas and inequalities for holomorphic mappings and solutions to elliptic PDEs in Banach spaces.

Contribution

It introduces new sharp Schwarz type estimates and boundary lemmas, extending classical results to Banach spaces and elliptic PDE contexts.

Findings

Improved Schwarz estimates for holomorphic mappings.

Sharp boundary Schwarz lemmas for Banach space mappings.

Refined bounds on subballs of the unit ball.

Abstract

The primary objective of this paper is to develop methodologies for investigating Schwarz type lemmas and to present their applications in Banach spaces. First, we improve upon the main results obtained by Osserman [Proc. Am. Math. Soc. 128: 3513-3517, 2000] and Chen et al. [J. Anal. Math. 152: 181-216, 2024]. Based on these sharp estimates, we then derive several sharp boundary Schwarz type lemmas (also known as Hopf type lemmas) for holomorphic mappings in Banach spaces, as well as for solutions to certain classes of elliptic partial differential equations on the Euclidean unit ball in $\mathbb{C}^n$ or on the unit disk in $\mathbb{C}$. Furthermore, we prove some sharp Schwarz type lemmas for holomorphic mappings that send a prescribed point to another prescribed point. Finally, these lemmas are applied to establish a sharp Minda type Schwarz inequality in Banach spaces and to provide a sharp refined bound on subballs of the unit ball.