Equality conditions for the fractional superadditive volume inequalities

Mark Meyer

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arXiv · 2307.07097

Equality conditions for the fractional superadditive volume inequalities

Mark Meyer

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Abstract

While studying set function properties of Lebesgue measure, F. Barthe and M. Madiman proved that Lebesgue measure is fractionally superadditive on compact sets in $\mathbb{R}^n$. In doing this they proved a fractional generalization of the Brunn-Minkowski-Lyusternik (BML) inequality in dimension $n=1$. In this paper we will prove the equality conditions for the fractional superadditive volume inequalites for any dimension. The non-trivial equality conditions are as follows. In the one-dimensional case we will show that for a fractional partition $(\mathcal{G},\beta)$ and nonempty sets $A_1,\dots,A_m\subseteq\mathbb{R}$, equality holds iff for each $S\in\mathcal{G}$, the set $\sum_{i\in S}A_i$ is an interval. In the case of dimension $n\geq2$ we will show that equality can hold if and only if the set $\sum_{i=1}^{m}A_i$ has measure $0$.

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Mark Meyer. 2023-07-14. Equality conditions for the fractional superadditive volume inequalities. https://arxiv.org/abs/2307.07097

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