Ilmanen's Lemma on Insertion of C${}^{1,1}$ Functions

Abstract

We give a proof of Ilmanen's lemma, which asserts that between a locally semi-convex and a locally semi-concave function it is possible to find a C${}^{1,1}$ function.

17 pages, 1 figure, accepted for publication in Rend. Semin. Mat. Univ. Padova