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 , whereas the one- and two-dimensional cases have remained unresolved. We construct two explicit -point subsets of the rank-two finite Abelian group : 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 that are finite unions of unit squares. Consequently, both implications in Fuglede's conjecture fail in dimension two.
Keywords
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