This paper considers the parameterized infinite dimensional optimization problem minimize{t≥0:  S∩{x+tF}≠∅},\hbox{minimize}\quad\bigl\{t\geq 0:\;S \cap\{x+tF\}\not= \emptyset\bigr\}, where SS is a nonempty closed subset of a Hilbert space HH and F⊆HF\subseteq H is closed convex satisfying 0∈int  F0\in \iint F. The optimal value T(x)T(x) depends on the parameter x∈Hx\in H, and the (possibly empty) set S∩(x+T(x)F)S\cap (x+T(x)F) of optimal solutions is the ``FF-projection'' of xx into SS. We first compute proximal and Fréchet subgradients of T(⋅)T(\cdot) in terms of normal vectors to level sets, and secondly, in terms of the FF-projection. Sufficient conditions are also obtained for the differentiability and semiconvexity of T(⋅)T(\cdot), results which extend the known case when FF is the unit ball

Contact details are reproduced from the original publication and may be historical.

Giovanni Colombo

Dip. di Matematica Pura e Applicata, Università di Padova, Via Belzoni 7, 35131 Padova, Italy

colombo@math.unipd.it

Peter R. Wolenski

Dept. of Mathematics, Louisiana State University, 326 Lockett Hall, Baton Rouge,
LA 70803-4918, U.S.A.

wolenski@math.lsu.edu
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G. Colombo, P. R. Wolenski. “Variational Analysis for a Class of Minimal Time Functions in Hilbert Spaces.” Journal of Convex Analysis 11 (2004), No. 2, 335–361. https://doi.org/10.68381/jca11021