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Concurrent normals conjecture for convex bodies in R^n

Establish that for every integer n ≥ 2 and every compact convex body P contained in R^n, there exists a point y in the interior of P that lies on at least 2n distinct inward normals to the boundary ∂P, each normal having a different base point on ∂P.

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Background

The paper opens by recalling a long-standing conjecture in the smooth setting relating normals to convex bodies: for any convex body in Rn, there should exist an interior point lying on at least 2n boundary normals. This classical conjecture is known to hold in low dimensions (n = 2, 3, 4), but remains unresolved in general.

The authors’ work focuses on the polyhedral (piecewise-linear) counterpart of this problem, connecting the count of normals to critical points of the squared distance function within a Morse-theoretic framework. Their results highlight differences between smooth bodies and polytopes, but they cite the smooth conjecture as a motivating open problem.

References

It is conjectured since long that for any convex body $P\subset \mathbb{R}n$ there exists a point in its interior which belongs to at least $2n$ normals from different points on the boundary of $P$. The conjecture is known to be true for $n=2,3,4$.

Concurrent normals problem for convex polytopes and Euclidean distance degree (2406.01773 - Nasonov et al., 3 Jun 2024) in Abstract