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Article Dans Une Revue American Journal of Mathematics Année : 2016

Convexity of level sets for elliptic problems in convex domains or convex rings: two counterexamples

Résumé

This paper deals with some geometrical properties of solutions of some semilinear elliptic equations in bounded convex domains or convex rings. Constant boundary conditions are imposed on the single component of the boundary when the domain is convex, or on each of the two components of the boundary when the domain is a convex ring. A function is called quasiconcave if its superlevel sets, defined in a suitable way when the domain is a convex ring, are all convex. In this paper, we prove that the superlevel sets of the solutions do not always inherit the convexity or ring-convexity of the domain. Namely, we give two counterexamples to this quasiconcavity property: the first one for some two-dimensional convex domains and the second one for some convex rings in any dimension.

Dates et versions

hal-00815552 , version 1 (19-04-2013)

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Citer

Francois Hamel, Nikolai Nadirashvili, Yannick Sire. Convexity of level sets for elliptic problems in convex domains or convex rings: two counterexamples. American Journal of Mathematics, 2016, 138 (2), pp.499-527. ⟨10.1353/ajm.2016.0012⟩. ⟨hal-00815552⟩
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