Bednařík, Dušan; Pastor, Karel A characterization of \(C^{1,1}\) functions via lower directional derivatives. (English) Zbl 1212.49043 Math. Bohem. 134, No. 2, 217-221 (2009). Summary: The notion of \(\tilde {\ell }\)-stability is defined using the lower Dini directional derivatives and was introduced by the authors in their previous papers. In this paper we prove that the class of \(\tilde {\ell }\)-stable functions coincides with the class of \(C^{1,1}\) functions. MSC: 49K40 Sensitivity, stability, well-posedness 26B05 Continuity and differentiation questions Keywords:\(\ell \)-stable function; \(\tilde {\ell }\)-stability × Cite Format Result Cite Review PDF Full Text: DOI