Betke–Weil reverse Alexandrov–Fenchel conjecture for mixed volumes

Let K1,,KmK_1,\ldots,K_m, with mnm\leq n, be compact convex sets in Rn\mathbb{R}^n, and let α1,,αmN\alpha_1,\ldots,\alpha_m\in\mathbb{N} satisfy α1++αm=n\alpha_1+\cdots+\alpha_m=n. Write V(K1[α1],,Km[αm])V(K_1[\alpha_1],\ldots,K_m[\alpha_m]) for the mixed volume with multiplicities αi\alpha_i, Vαi(Ki)V_{\alpha_i}(K_i) for the intrinsic volume of order αi\alpha_i, and (nα1,,αm)\binom{n}{\alpha_1,\ldots,\alpha_m} for the multinomial coefficient.

Betke–Weil conjecture.

(nα1,,αm)V(K1[α1],,Km[αm])Vα1(K1)Vαm(Km).\binom{n}{\alpha_1,\ldots,\alpha_m}V(K_1[\alpha_1],\ldots,K_m[\alpha_m])\leq V_{\alpha_1}(K_1)\cdots V_{\alpha_m}(K_m).

If dim(Ki)αi\dim(K_i)\geq\alpha_i for i=1,,mi=1,\ldots,m, equality holds if and only if dim(Ki)=αi\dim(K_i)=\alpha_i for i=1,,mi=1,\ldots,m and the affine hulls of K1,,KmK_1,\ldots,K_m are pairwise orthogonal.

This is a reverse counterpart to the Alexandrov–Fenchel inequality and gives the sharp upper bound suggested by Ulrich Betke and Wolfgang Weil. The supplied text does not provide evidence that the conjecture has been resolved.

Sources & referencesView supporting material

Primary source

Károly J. Böröczky and Daniel Hug, “Reverse Alexandrov–Fenchel inequalities for zonoids”, arXiv:2106.13143 (2021).

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