On the relation between distances and seminorms on Fréchet spaces, with application to isometries

Isabelle Chalendar, Lucas Oger, Jonathan R. Partington

Published 2025-06-20Version 1

A study is made of linear isometries on Fr\'echet spaces for which the metric is given in terms of a sequence of seminorms. This establishes sufficient conditions on the growth of the function that defines the metric in terms of the seminorms to ensure that a linear operator preserving the metric also preserves each of these seminorms. As an application, characterizations are given of the isometries on various spaces including those of holomorphic functions on complex domains and continuous functions on open sets, extending the Banach--Stone theorem to surjective and nonsurjective cases.