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Equivalence among various derivatives and subdifferentials of the distance function. (English) Zbl 1035.49019

Let \(X\) be a normed linear space with uniformly Gâteaux differentiable norm and \(C\) a nonempty closed subset of \(X\). The authors study differentiability properties of the distance function \(d_C\) associated with \(C\). For example, it is shown that \(d_C\) is strictly differentiable at \(x\in X\setminus C\) if and only if \(d_C\) is regular at \(x\) in the sense of F. H. Clarke. Further equivalent conditions are established involving various subdifferentials. Moreover, if \(X\) is a Hilbert space, then the Fréchet differentiability of \(d_C\) is characterized, among others, in terms of the metric projection \(P_C\) of \(C\).
The results are based on and complement those obtained earlier by J. M. Borwein, S. P. Fitzpatrick and J. R. Giles [J. Math. Anal. Appl. 128, 512–534 (1987; Zbl 0644.46032)], F. H. Clarke, R. J. Stern and P. R. Wolenski [J. Convex Anal. 2, No. 1–2, 117–144 (1995; Zbl 0881.49008)], S. Fitzpatrick [Bull. Aust. Math. Soc. 22, 291–312 (1980; Zbl 0437.46012)], and others.

MSC:

49J52 Nonsmooth analysis
49J50 Fréchet and Gateaux differentiability in optimization
Full Text: DOI

References:

[1] Borwein, J. M.; Fitzpatrick, S. P.; Giles, J. R., The differentiability of real functions on normed linear space using generalized subgradients, J. Math. Anal. Appl., 128, 512-534 (1987) · Zbl 0644.46032
[2] Burke, J. V.; Ferris, M. C.; Qian, M., On the Clarke subdifferential of the distance function of a closed set, J. Math. Anal. Appl., 166, 199-213 (1992) · Zbl 0761.49009
[3] Clarke, F. H., Optimization and Nonsmooth Analysis (1983), Wiley-Interscience: Wiley-Interscience New York · Zbl 0727.90045
[4] Clarke, F. H.; Stern, R. J.; Wolenski, P. R., Proximal smoothness and the lower-\(C^2\) property, J. Convex Anal., 2, 117-144 (1995) · Zbl 0881.49008
[5] Clarke, F. H.; Ledyaev, Yu. S.; Wolenski, P. R., Proximal analysis and minimization principles, J. Math. Anal. Appl., 196, 722-735 (1995) · Zbl 0865.49015
[6] Clarke, F. H.; Ledyaev, Yu. S.; Stern, R. J.; Wolenski, P. R., Nonsmooth Analysis and Control Theory. Nonsmooth Analysis and Control Theory, Graduate Texts in Mathematics, 178 (1998), Springer: Springer New York · Zbl 1047.49500
[7] Craven, B. D.; Ralph, D.; Glover, B. M., Small convex-valued subdifferentials in mathematical programming, Optimization, 32, 1-21 (1995) · Zbl 0816.49007
[8] Fitzpatrick, S., Metric projections and the differentiability of distance functions, Bull. Austral. Math. Soc., 22, 291-312 (1980) · Zbl 0437.46012
[9] Michel, P.; Penot, J. P., Calcul sous-différentiel pour les fonctions Lipschitziennes et non Lipschitziennes, C. R. Acad. Sci. Paris, 298, 269-272 (1984) · Zbl 0567.49008
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