Breakthrough Tracker record

Both directions of Fuglede’s conjecture fail in dimension two

The paper gives two explicit 60-point constructions in a finite abelian group and transfers them to bounded subsets of the plane. One planar set tiles by translations but is not spectral; the other is spectral but does not tile.

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Stable ID
math-fuglede-dimension-two-counterexamples-2026
Revision
math-fuglede-dimension-two-counterexamples-2026.v1
Field
Mathematics · Harmonic analysis and combinatorics
Evidence
Tier 1 · Peer reviewed: No
Record state
Provisional · Provisional preprint claim
Last checked

AI role

No AI role was disclosed in the inspected manuscript.

Record details

Problem or result
Fuglede’s conjecture in the two-dimensional unrestricted measurable setting
Authors
Tao Zhang
Institutions
Xidian University
Result date
Preprint submitted July 17, 2026

Why it matters

Counterexamples were already known in dimensions three and higher, while the unrestricted two-dimensional case had remained unresolved.

Limits

This is a first-version preprint without located independent specialist assessment or peer review. The result concerns unrestricted measurable sets in the plane; narrower versions of Fuglede’s problem can remain open.

Sources

  1. Primary: Tao Zhang, Both directions of Fuglede's conjecture fail in dimension two

Correction and revision history

  1. 2026-07-23 — Prepared as a provisional tracker addition after checking the explicit constructions and the stated finite-to-infinite transfer; independent assessment remains pending.

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