English

Both directions of Fuglede's conjecture fail in dimension two

Combinatorics 2026-07-17 v1 Classical Analysis and ODEs

Abstract

Fuglede's conjecture asserts that a measurable set of positive and finite measure is spectral if and only if it tiles Euclidean space by translations. Counterexamples are known in every dimension d3d\ge3, whereas the one- and two-dimensional cases have remained unresolved. We construct two explicit 6060-point subsets of the rank-two finite Abelian group Z60×Z12\Z_{60}\times\Z_{12}: one is a translational tile with no spectrum, and the other is spectral but does not tile. A finite-to-infinite transference principle lifts them to bounded subsets of R2\R^2 that are finite unions of unit squares. Consequently, both implications in Fuglede's conjecture fail in dimension two.

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Cite

@article{arxiv.2607.15632,
  title  = {Both directions of Fuglede's conjecture fail in dimension two},
  author = {Tao Zhang},
  journal= {arXiv preprint arXiv:2607.15632},
  year   = {2026}
}

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18 pages