We generalize a recent result of C. Nour, H. Saoud and J. Takche [Regularization via sets satisfying the interior sphere condition, J. Convex Analysis 25(1) (2018) 1–19], where the authors provided an inner approximation of a subset S of the n-dimensional real space Rn\mathbb{R}^n by sets satisfying the interior sphere condition. The main idea is to replace the convex cones used there by curved ones which leads us to weaken the assumptions and cover more sets S.

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

Chadi Nour

Dept. of Computer Science and Mathematics, Lebanese American University, Byblos, Lebanon

cnour@lau.edu.lb

Jean Takche

Dept. of Computer Science and Mathematics, Lebanese American University, Byblos, Lebanon

jtakchi@lau.edu.lb
  1. A. Canino: On p-convex sets and geodesics, J. Differential Equations 75(1) (1988) 118–157.https://doi.org/10.1016/0022-0396(88)90132-5Google Scholar
  2. P. Cannarsa, H. Frankowska: Interior sphere property of attainable sets and time optimal control problems, ESAIM: Control Optim. Calc. Var. 12 (2006) 350–370.https://doi.org/10.1051/cocv:2006002Google Scholar
  3. P. Cannarsa, C. Sinestrari: Convexity properties of the minimum time function, Calc. Var. 3 (1995) 273–298.https://doi.org/10.1007/BF01189393Google Scholar
  4. P. Cannarsa, C. Sinestrari: Semiconcave Functions, Hamiton-Jacobi Equations and Optimal Control, Birkhäuser, Boston (2004).https://doi.org/10.1007/b138356Google Scholar
  5. F. H. Clarke, Yu. Ledyaev, R. J. Stern, P. R. Wolenski: Nonsmooth Analysis and Control Theory, Graduate Texts in Mathematics 178, Springer, New York (1998).Google Scholar
  6. F. H. Clarke, R. J. Stern, P. R. Wolenski: Proximal smoothness and the lower-C 2 property, J. Convex Analysis 2(1/2) (1995) 117–144.https://doi.org/10.68381/jca02008Google Scholar
  7. H. Federer: Curvature measures, Trans. Amer. Math. Soc. 93 (1959) 418–491.https://doi.org/10.1090/S0002-9947-1959-0110078-1Google Scholar
  8. G. Colombo, A. Marigonda: Differentiability properties for a class of non-convex functions, Calc. Var. 25 (2005) 1–31.https://doi.org/10.1007/s00526-005-0352-7Google Scholar
  9. G. Colombo, A. Marigonda, P. R. Wolenski: Some new regularity properties for the minimal time function, SIAM J. Control Optim. 44(6) (2006) 2285–2299.https://doi.org/10.1137/050630076Google Scholar
  10. G. Colombo, K. T. Nguyen: On the structure of the minimum time function, SIAM J. Control Optim. 48(7) (2010) 4776–4814.https://doi.org/10.1137/090774549Google Scholar
  11. K. T. Nguyen: Hypographs satisfying an external sphere condition and the regularity of the minimum time function, J. Math. Anal. Appl. 372(2) (2010) 611–628.https://doi.org/10.1016/j.jmaa.2010.07.010Google Scholar
  12. C. Nour, H. Saoud, J. Takche: Regularization via sets satisfying the interior sphere condition, J. Convex Analysis 25(1) (2018) 1–19.https://doi.org/10.68381/jca25001Google Scholar
  13. C. Nour, R. J. Stern, J. Takche: The union of uniform closed balls conjecture, Control and Cybernetics 38(4B) (2009) 1525–1534.Google Scholar
  14. C. Nour, R. J. Stern, J. Takche: The θ-exterior sphere condition, φ-convexity and local semiconcavity, Nonlinear Analysis 73(2) (2010) 573–589.https://doi.org/10.1016/j.na.2010.04.001Google Scholar
  15. C. Nour, R. J. Stern, J. Takche: Validity of the union of uniform closed balls conjecture, J. Convex Analysis 18(2) (2011) 589–600.https://doi.org/10.68381/jca18037Google Scholar
  16. C. Nour, J. Takche: On the union of closed balls property, J. Optim. Theory Appl. 155(2) (2012) 376–389.https://doi.org/10.1007/s10957-012-0068-8Google Scholar
  17. C. Nour, J. Takche: A new class of sets regularity, J. Convex Analysis 25(4) (2018) 1059–1074.https://doi.org/10.68381/jca25068Google Scholar
  18. J.-P. Penot: Calculus Without Derivatives, Graduate Texts in Mathematics 266, Springer, New York (2013).https://doi.org/10.1007/978-1-4614-4538-8Google Scholar
  19. R. A. Poliquin, R. T. Rockafellar: Prox-regular functions in variational analysis, Trans. Amer. Math. Soc. 348 (1996) 1805–1838.https://doi.org/10.1090/S0002-9947-96-01544-9Google Scholar
  20. R. A. Poliquin, R. T. Rockafellar, L. Thibault: Local differentiability of distance functions, Trans. Amer. Math. Soc. 352 (2000) 5231–5249.https://doi.org/10.1090/S0002-9947-00-02550-2Google Scholar
  21. R. T. Rockafellar, R. J.-B. Wets: Variational Analysis, Grundlehren der Mathematischen Wissenschaften 317, Springer, Berlin (1998).https://doi.org/10.1007/978-3-642-02431-3Google Scholar
  22. C. Sinestrari: Semiconcavity of the value function for exit time problems with nonsmooth target, Commun. Pure Appl. Analysis 3(4) (2004) 757–774.https://doi.org/10.3934/cpaa.2004.3.757Google Scholar

C. Nour, J. Takche. “A General Result About Inner Regularization of Sets.” Journal of Convex Analysis 27 (2020), No. 3, 943–958. https://doi.org/10.68381/jca27048