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arXiv · 2508.17409

Generalized convexity of the Lambert $W$ function

Gendi Wang
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Abstract

This paper investigates the generalized convexity properties of the Lambert $W$ function, defined as the solution to $W(z)e^{W(z)}=z$. Focusing on $H_{p,q}$-convexity and concavity with respect to H\"older means, we derive necessary and sufficient conditions for $W$ to exhibit strict $H_{p,q}$-convexity or concavity on the interval $(0,+\infty)$. The main result characterizes these properties in terms of specific parameter regions $(p,q)$-plane. Inequalities involving harmonic, geometric, and arithmetic means are established, with equalities holding only when $x=y$.

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Gendi Wang. 2025-08-24. Generalized convexity of the Lambert $W$ function. https://arxiv.org/abs/2508.17409

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