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Complement Submodular Information Measures for Balanced and Robust Data Selection A Proof of a Conjecture on Positive and Negative Square Energies of Unicyclic Graphs Laplacian Spectrum of the Weakly Zero-Divisor Graph of a Finite Commutative Ring An identity for second Eulerian numbers via lattice-point counting $t$-tone edge coloring of graphs Constructing Maximal Bumpless Pipedreams for Double Grothendieck Polynomials Mubayi's Polynomial-Ideal Conjecture and Cover-Ideal Turán Methods Implicit Binarization via Complex Phase Dynamics in Combinatorial Optimization The limits of Schur multipliers in Pólya conversion problems for the $q$-permanent function Universality theorems for generalized splines Framing Triangulations for Arbitrary Integer Flow Polytopes On the Common Generalization of Gentle Algebras and Framed Directed Acyclic Graphs The complexity of frugal digraph homomorphisms Chaotic and periodic behavior of jeu de taquin on infinite Young tableaux Enumerating Pattern Avoiding Parking Functions Incidence toric ideals and three-point functions Unique Winning Opening Move in Three-Row Chomp Strong majority colorings of graphs A Balancing Theorem for Spanning Trees of Rectangular Grid Graphs Spectral radius and edge-disjoint connected factors of graphs New invariants for rank metric codes, with applications to the classification of rank two semifields of order 256 Flexible DP-4-coloring of planar graphs without 4-cycles and intersecting triangles Balanced intersection size distributions in projective planes List Reconstruction Problem with List Size Two Is Dimensionality a Barrier for Retrieval Models? The INIEP: Irreducible and Positive Realizations The number of Pfaffian orientations on punctured polygonally cellulated surfaces Explicit Construction of Polytopes whose Ehrhart Polynomials Realize any Given Sign Pattern Finite-state enumeration of adjacency-constrained 132-avoiding permutations AMDS and quantum AMDS Constacyclic codes of length $4p^ς$ over $\mathbb{F}_{{p}^{m}}$
Sub-25-dimensional counterexamples to Borsuk's conjecture...
Thomas Jenrich · 2023-05-11 · via math.CO updates on arXiv.org

In 1933, Karol Borsuk asked whether each bounded set in the $n$-dimensional Euclidean space can be divided into $n$+1 parts of smaller diameter. Because it would not make sense otherwise, one usually assumes that he just forgot to require that the whole set contains at least two points. The hypothesis that the answer to that question is positive became famous under the name \emph{Borsuk's conjecture}. Counterexamples are known for any $n\ge 64$, since 2013. Let $Λ$ be the (original, unscaled) Leech lattice, a now very well-known infinite discrete vector set in the 24-dimensional Euclidean space. The smallest norm of nonzero vectors in $Λ$ is $\sqrt{32}$. Let $M$ be the set of the 196560 vectors in $Λ$ having this norm. For each $x \in M$, $-x$ is in $M$. Let $H$ be the set of all subsets of $M$ that for each $x$ in $M$ contain either $x$ or $-x$. Each element of $H$ has the same diameter $d = \sqrt{96}$. For dimensions $n<24$ one can analogously construct respective $M_n$ and $H_n$ from laminated $n$-dimensional sublattices $Λ_n$ of $Λ$. For uniformity, let $Λ_{24}=Λ$, $M_{24} = M$ and $H_{24} = H$. If $M_n$ is divisible into at most $n+1$ parts of diameter below $d$ then this applies to all elements of $H_n$, too. I have checked that this is the case for all $n \le 21$. For $n$ from 22 to 24, the minimum number of parts of diameter below $d$ that I was able to divide $M_n$ into are 25, 29 and 34, resp. The source package of this article contains a data file encoding an element of $H_{24}=H$ that I can not divide into less than 29 parts of smaller diameter.