Extending functions from a neighborhood of the sphere to the ball

Abstract

In this article, we are interested in the problem of extending the germ of a smooth function $\tilde{f}$ defined along the standard sphere of dimension $n$ to a function defined on the ball which has no critical points. The article gives a necessary condition using the Morse chain complex associated to the function $f$, restriction of $\tilde{f}$ to the sphere $\mathbb{S}^n$, which is assumed to be a Morse function.