128 research outputs found
Inf-convolution and regularization of convex functions on Riemannian manifolds of nonpositive curvature
We show how an operation of inf-convolution can be used to approximate convex
functions with smooth convex functions on Riemannian manifolds with
nonpositive curvature (in a manner that not only is explicit but also preserves
some other properties of the original functions, such as ordering, symmetries,
infima and sets of minimizers), and we give some applications.Comment: 17 page
Uniform approximation of continuous functions by smooth functions with no critical points on Hilbert manifolds
We prove that every continuous function on a separable infinite-dimensional
Hilbert space X can be uniformly approximated by smooth functions with no
critical points. This kind of result can be regarded as a sort of very strong
approximate version of the Morse-Sard theorem. Some consequences of the main
theorem are as follows. Every two disjoint closed subsets of X can be separated
by a one-codimensional smooth manifold which is a level set of a smooth
function with no critical points; this fact may be viewed as a nonlinear
analogue of the geometrical version of the Hahn-Banach theorem. In particular,
every closed set in X can be uniformly approximated by open sets whose
boundaries are smooth one-codimensional submanifolds of X. Finally, since every
Hilbert manifold is diffeomorphic to an open subset of the Hilbert space, all
of these results still hold if one replaces the Hilbert space X with any smooth
manifold M modelled on X.Comment: 24 page
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