arXiv:2504.19899v3
Abstract
In this work we give a full characterization of sets of multiple polynomial recurrence in Weyl systems, which are ergodic unipotent affine transformations on products of tori and finite abelian groups. In particular, we show that measurable and topological recurrence in Weyl systems coincide. Our analysis also yields a structure theorem for polynomial multicorrelation sequences in Weyl systems. These results stem from an in-depth study of the Weyl complexity of a set of polynomials and the introduction of a new concept: the \textit{Weyl polynomials} generated by a set of polynomials.
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01Statements2 reported findingsNo statement issues found
The current Weyl-system recurrence characterization, stabilization threshold, polynomial-frequency structure, and uncorrelatedness criterion are supported. Extensions to arbitrary systems are retained as conjectures or explicitly conditional consequences.
Weyl polynomial spaces control the claimed recurrence and correlation structure
PDF pp. 13–23, 31–35 · arXiv:2504.19899v3
The annihilator condition on the polynomial matrix identifies precisely the frequencies surviving integration of characters. Its rational linear algebra gives integral bases and stabilization at the Weyl complexity. Rectangular Fourier truncations approximate each bounded function in the required finite norm, uniformly controlling the resulting correlations; surviving character products have the stated polynomial phases and square-summable coefficient sequence. This is enough for the liminf-of-uniform-tail approximation asserted in the structure theorem.
Both directions of the recurrence and independence equivalences check
PDF pp. 25–27, 32–36 · arXiv:2504.19899v3
Disjoint rational polynomial spaces prevent cancellation of irrational phase coefficients, while a common nonzero integral polynomial produces correlated character examples. Topological recurrence near zero forces all finitely many Weyl frequencies near zero. Conversely the IP recurrence lower bound ensures positivity near the zero polynomial phase, and Kronecker recurrence chooses arbitrarily large indices with those phase constraints. A polynomial outside one Weyl space gives the explicit separating set used for optimality and the inclusion criterion.
02Proofs2 reported findingsNo proof issues found
The Kronecker-preserving extension, Fourier estimates, and reduction through finite connected components close the principal proof chain in v3.
The algebraic extension and polynomial-basis changes preserve the required data
PDF pp. 8–10, 16–17 · arXiv:2504.19899v3
Connectedness of the kernel makes the Smith-normal-form diagonal entries of the Kronecker factor map equal to one, supplying an integral right inverse. The columns span the ambient space and intertwine the unipotent maps; the affine translation adjustment then gives a surjective factor with the same Kronecker rotation. Vandermonde's identity supplies the displayed invertible change from binomial to divided-power polynomial matrices.
Residue restrictions and the connected-component reduction do not lose recurrence
PDF pp. 23–25, 33–34 · arXiv:2504.19899v3
A sufficiently divisible progression makes all shifted, divided polynomials integral. The invariance of Weyl polynomial membership under that change is established before its use. Partition regularity selects a residue class retaining the full Kronecker recurrence property, and a finite rotation forces every relevant exponent to preserve the connected component. The matrix has nonzero determinant , so its torus map is onto and produces an ergodic affine root of the return map. The connected proof consequently applies with all required divisibility and measure factors intact.
03Novelty0 reported findingsNo novelty concerns found
No non-novelty findings.