On global inverse and implicit functions

Abstract

Since the Hadamard Theorem, several metric and topological conditions have emerged in the literature to date, yielding global inversion and implicit theorems for functions in different settings. Relevant examples are the mappings between infinite-dimensional Banach-Finsler manifolds, which are the focus of this work. Emphasis is given to the nonlinear Fredholm operators of nonnegative index between Banach spaces. The results are based on good local behavior of $f$ at every $x$, namely: $f$ is a local homeomorphism or $f$ is locally equivalent to a projection. The general structure includes a condition that ensures a global property for the fibres of $f$, ideally, expecting to conclude that $f$ is a global diffeomorphism or equivalent to a global projection. A review of such these results and some relationships between different criteria are shown. Also, in this context, a global version of Graves Theorem is obtained.