Using advanced concepts and techniques from convex and variational analysis (such as the notion of twice epi-differentiability), we establish, under a set of appropriate conditions (including a polyhedricity assumption), that the solution to a parameterized nonlinear variational inequality associated with a positively homogeneous function is differentiable, and furthermore that its derivative is the solution to a corresponding complementarity problem. We illustrate our main result through a series of examples and counterexamples. In particular we introduce an example of a projection operator onto a nonempty closed convex cone that is not directionally differentiable, which is, to our best knowledge, new in the literature.

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Samir Adly

Institut de Recherche XLIM, UMR CNRS 7252, Université de Limoges, Limoges, France

samir.adly@unilim.fr

Loïc Bourdin

Institut de Recherche XLIM, UMR CNRS 7252, Université de Limoges, Limoges, France

loic.bourdin@unilim.fr
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S. Adly, L. Bourdin. “The Derivative of a Nonlinear Positively Homogeneous Variational Inequality is a Complementarity Problem.” Journal of Convex Analysis 33 (2026), No. 1&2, 455–472. https://doi.org/10.68381/jca33029