The Hadwiger Number of a Starlike Disk Can Exceed Eight

We construct a starlike topological disk S with nine pairwise nonoverlapping translates, each touching S. This disproves the conjecture of A. Bezdek, K. Kuperberg and W. Kuperberg that H(S) ≤ 8 for every starlike disk. The body is the union of fifteen convex polygons with integer coordinates and a common nondegenerate triangular core. Nine point identities exhibit intersections between S and its nine translates. An exhaustive integer calculation supplies separating lines for all 10,125 pairs of convex pieces belonging to distinct copies among these ten disks, proving interior disjointness without numerical tolerances. Together, these checks establish the required contacts and nonoverlap. We provide the full coordinate data, the topological argument and a reproducible exact-arithmetic certificate verifier. The result establishes H(S) ≥ 9; it does not determine H(S) exactly. Independent expert review is invited; the result has not yet undergone peer review.

Authors

Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-09-09
DOI
https://doi.org/10.5281/zenodo.22667896
Primary Topic
Advanced Combinatorial Mathematics
Type
preprint
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preprint

The Hadwiger Number of a Starlike Disk Can Exceed Eight

John Seamons
Zenodo (CERN European Organization for Nuclear Research)
Advanced Combinatorial Mathematics
preprint

The Hadwiger Number of a Starlike Disk Can Exceed Eight

John Seamons
preprint en

Abstract

We construct a starlike topological disk S with nine pairwise nonoverlapping translates, each touching S. This disproves the conjecture of A. Bezdek, K. Kuperberg and W. Kuperberg that H(S) ≤ 8 for every starlike disk. The body is the union of fifteen convex polygons with integer coordinates and a common nondegenerate triangular core. Nine point identities exhibit intersections between S and its nine translates. An exhaustive integer calculation supplies separating lines for all 10,125 pairs of convex pieces belonging to distinct copies among these ten disks, proving interior disjointness without numerical tolerances. Together, these checks establish the required contacts and nonoverlap. We provide the full coordinate data, the topological argument and a reproducible exact-arithmetic certificate verifier. The result establishes H(S) ≥ 9; it does not determine H(S) exactly. Independent expert review is invited; the result has not yet undergone peer review.

Zenodo (CERN European Organization for Nuclear Research)
Advanced Combinatorial Mathematics
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