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arXiv 1507.00765math.MGmath.FA
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混合体积的Bezout不等式

Bezout Inequality for Mixed volumes

Ivan Soprunov, Artem Zvavitch

摘要:

本文考虑了混合体积Bezout不等式的类似结果:$$V(P_1,\dots,P_r,Δ^{n-r})V_n(Δ)^{r-1}\leq \prod_{i=1}^r V(P_i,Δ^{n-1})\ \text{ for }2\leq r\leq n.$$我们证明了当$Δ$是$n$维单形且$P_1, \dots, P_r$是$\mathbb{R}^n$中的凸体时,上述不等式成立.我们猜想,如果上述不等式对所有凸体$P_1, \dots, P_r$成立,则$Δ$必是$n$维单形.我们证明了如果上述不等式对所有凸体$P_1, \dots, P_r$成立,则$Δ$必须是不可分解的(即不能写为两个与$Δ$不相似的凸体的Minkowski和),这证实了当$Δ$是一个简单多面体且在二维情况下的猜想.最后,我们将该不等式与一个关于凸体正交投影体积的不等式联系起来,并证明了该不等式的一个同构形式。

英文摘要:

In this paper we consider the following analog of Bezout inequality for mixed volumes: $$V(P_1,\dots,P_r,Δ^{n-r})V_n(Δ)^{r-1}\leq \prod_{i=1}^r V(P_i,Δ^{n-1})\ \text{ for }2\leq r\leq n.$$ We show that the above inequality is true when $Δ$ is an $n$-dimensional simplex and $P_1, \dots, P_r$ are convex bodies in $\mathbb{R}^n$. We conjecture that if the above inequality is true for all convex bodies $P_1, \dots, P_r$, then $Δ$ must be an $n$-dimensional simplex. We prove that if the above inequality is true for all convex bodies $P_1, \dots, P_r$, then $Δ$ must be indecomposable (i.e. cannot be written as the Minkowski sum of two convex bodies which are not homothetic to $Δ$), which confirms the conjecture when $Δ$ is a simple polytope and in the 2-dimensional case. Finally, we connect the inequality to an inequality on the volume of orthogonal projections of convex bodies as well as prove an isomorphic version of the inequality.

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