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First page of Coven-Meyerowitz T2 necessity through coprime stripe collapse

Coven-Meyerowitz T2 necessity through coprime stripe collapse

Jitendra Prajapati

math.GM Sep 12, 2026 · v1
The unrestricted Coven–Meyerowitz T2 necessity theorem for finite integer tiles is formalized in Lean 4.23.0 with a pinned Mathlib commit.
We prove that every finite subset of the integers which tiles by translations satisfies the Coven-Meyerowitz condition T2, with no restriction on the number of prime factors or their exponents. Together with the necessity of T1 and the sufficiency of T1 and T2 proved by Coven and Meyerowitz, this gives their proposed characterization of finite integer tiles. The proof uses strong induction on a cyclic tiling period. Character identities produce periodic Boolean product stripes; integral descent to a coprime quotient and the Frobenius identity force a common orientation. Independent phase shifts then give smaller-period tilings from which the mixed cyclotomic zeros of the original factors can be recovered. A companion Lean formalization verifies the unrestricted T2 necessity statement.

Coven and Meyerowitz proposed characterizing finite integer translational tiles by two cyclotomic conditions, T1 and T2. T1 was known to be necessary and T1 plus T2 sufficient, but T2 necessity was known only when |A| has at most two distinct prime factors.

The proof first reduces an integer tiling to a cyclic tiling, then uses strong induction on the cyclic period. Character identities on prime fibers produce periodic Boolean product stripes. Descent to a coprime quotient and a Frobenius identity in F_p[G] force a common row orientation. Independent phase shifts then give tilings of smaller period, from which the mixed cyclotomic zeros of the original factors are recovered.

Every finite tile of the integers satisfies T2, with no restriction on prime factors or exponents. Combined with the classical results, this gives the full Coven–Meyerowitz characterization of finite integer tiles. A companion Lean development verifies the T2 necessity theorem, while the two classical implications are cited rather than formalized.