Whitney's and Seeley's type of extensions for maps defined on some Banach spaces (1910.14248v2)

Abstract: Let $X=C[0,1]$, and $Y$ be an arbitrary Banach space. Consider a collection of open segments ${V_i }\subset X$. Suppose the map $f: \cup_i V_i \to Y$ has $q$ bounded Fr\'echet derivatives ($q=0,1,...,\infty$), and $f$ and all its derivatives have continuous bounded limits at the boundary. Then, subject to some non-intercept condition for the segments $V_i$, the map $f$ can be extended to $F: X\to Y$, so that $F_{|\,\cup_i V_i}=f$ and $F$ has $q$ bounded derivatives. We prove similar Whitney's Extension theorem generalizations for some other Banach spaces. We also prove Seeley Extension theorem for $X=C[0,1].$ These results are related to the problems of function approximation, and manifold learning, which are of central importance to many applied fields.