Continuous selections of Lipschitz extensions in metric spaces

This paper deals with the study of parameter dependence of extensions of Lipschitz mappings from the point of view of continuity. We show that if assuming appropriate curvature bounds for the spaces, the multivalued extension operators that assign to every nonexpansive (resp. Lipschitz) mapping all its nonexpansive extensions (resp. Lipschitz extensions with the same Lipschitz constant) are lower semi-continuous and admit continuous selections. Moreover, we prove that Lipschitz mappings can be extended continuously even when imposing the condition that the image of the extension belongs to the closure of the convex hull of the image of the original mapping. When the target space is hyperconvex one can obtain in fact nonexpansivity.Dirección General de Enseñanza SuperiorJunta de AndalucíaRomanian Ministry of Educatio

On smooth extensions of vector-valued functions defined on closed subsets of Banach spaces

Let and be Banach spaces, a closed subset of and a mapping . We give necessary and sufficient conditions to obtain a smooth mapping such that , when either (i) and are Hilbert spaces and is separable, or (ii) is separable and is an absolute Lipschitz retract, or (iii) and with , or (iv) and with , where is any separable Banach space with a -finite measure space