arXiv:2504.17555v2

Coexistence of mixing and rigid behaviors in ergodic theory

Rigoberto Zelada

math.DS37A0537A4605D1047A3547B15

Paper metadata

Original submission: April 24, 2025
Latest revision: July 16, 2026 · version 2
Claimed MSC: 37A05, 37A46, 05D10, 47A35, 47B15
arXiv categories: math.DS
Paper license: CC BY 4.0 ↗
Comments: 36 pages, referees' comments included, error in proof of Corollary 1.10 corrected. To appear in Ergodic Theory and Dynamical Systems

Abstract

In this paper we introduce and explore the notion of rigidity group, associated with a collection of finitely many sequences, and show that this concept has many, somewhat surprising characterizations of algebraic, spectral, and unitary nature. Furthermore, we demonstrate that these characterizations can be employed to obtain various results in the theory of generic Lebesgue-preserving automorphisms of $[0,1]$ , IP-ergodic theory, multiple recurrence, additive combinatorics, and spectral theory. As a consequence of one of our results we show that given $(b_1,...b_\ell)\in\mathbb N^\ell$ , there is no orthogonal vector $(a_1,\dots,a_\ell)\in\mathbb Z^\ell$ with some $|a_j|=1$ if and only if there is an increasing sequence of natural numbers $(n_k)_{k\in\mathbb N}$ with the property that for each $F\subseteq \{1,...,\ell\}$ there is a $μ$ -preserving transformation $T_F:[0,1]\rightarrow[0,1]$ ( $μ$ denotes the Lebesgue measure) such that for any measurable $A,B\subseteq [0,1]$ , $\lim_{k\rightarrow\infty}μ(A\cap T_F^{-b_jn_k}B)=\begin{cases} μ(A\cap B),\,\text{ if }j\in F,\\ μ(A)μ(B),\,\text{ if }j\not\in F. \end{cases}$ We remark that this result has a natural extension to a wide class of families of sequences.

AI-generated audit

Audit summary

Audited against arXiv v2

Not a correctness certificate. A “Correct” result may include yellow typos or minor formal corrections that do not affect substantive soundness. It means this audit found no unresolved substantive error under the stated criteria; it does not replace expert scrutiny or formal verification.

Current report

Detailed mathematical audit

Generated August 18, 2026

01Statements3 reported findingsCorrect

Both main results are supported. Theorem 1.5 proves equivalence between the algebraic asymptotic-relation condition and the spectral, measure, unitary, and generic dynamical descriptions of rigidity groups. Theorem 1.8 uses the resulting continuous spectral measures to construct weakly mixing transformations that are rigid along prescribed sequences while having the announced mixing behavior along the complementary sequences.

Theorem 1.5Correct

Equivalent characterizations of rigidity groups

Pages 4–8 · Theorems 1.5 and 1.8 · arXiv:2504.17555v2

Theorem 1.5 identifies the groups that occur as rigidity groups through the printed algebraic condition on the subgroup of asymptotic relations. It proves equivalence with the spectral-measure, unitary-representation, and generic measure-preserving-transformation formulations listed in the statement. The implication from the algebraic condition constructs a continuous probability measure whose Fourier transform tends to one exactly along the prescribed sequences; the converse reads every forced asymptotic relation from that convergence. The quantifiers over sequences and integer combinations agree in all formulations.

Theorem 1.8Correct

Coexistence of prescribed mixing and rigidity

Pages 7–8 and 22–29 · Theorem 1.8 · arXiv:2504.17555v2

Under the algebraic compatibility condition stated in the theorem, the constructed continuous measure has Fourier coefficients tending to one on every rigidity sequence and to the target mixing limits on the complementary sequences. The Gaussian realization is weakly mixing because the measure is atomless. Its correlations inherit those Fourier limits, giving rigidity and mixing on the same transformation with the interpolation parameters exactly as prescribed.

Generic formulationCorrect

Passage from one realization to a residual class

Pages 16–22 · genericity propositions · arXiv:2504.17555v2

Finite correlation requirements are open in the weak topology and can be met densely by conjugating the spectral/Gaussian models on large Rokhlin towers. Intersecting the countable family of open dense conditions gives the residual set claimed in Theorem 1.5. The sequences are countable and fixed before the intersection, so the Baire argument has the correct quantifier order.

02Proofs3 reported findingsCorrect

Theorem 3.1 and the Gaussian realization. A maximal asymptotically independent subfamily defines an integer homomorphism whose kernel is exactly the subgroup of forced asymptotic relations. Fourier limits of the constructed measures equal one on this kernel and vanish or take the specified values off it. Passing to the annihilator compact group identifies the limiting measure with Haar measure. The spectral theorem realizes the measures as unitary correlations, and the Gaussian functor converts the continuous spectral representation into a weakly mixing probability-preserving transformation while preserving the selected rigidity times.

Reduction to asymptotically independent sequencesCorrect and complete

Theorem 3.1 and the Gaussian realization

Pages 10–29 · Sections 2–5 · arXiv:2504.17555v2

A maximal asymptotically independent subfamily defines an integer homomorphism whose kernel is exactly the subgroup of forced asymptotic relations. Fourier limits of the constructed measures equal one on this kernel and vanish or take the specified values off it. Passing to the annihilator compact group identifies the limiting measure with Haar measure. The spectral theorem realizes the measures as unitary correlations, and the Gaussian functor converts the continuous spectral representation into a weakly mixing probability-preserving transformation while preserving the selected rigidity times.

Sections 2–3Correct and complete

Asymptotic relations and Fourier limits

Pages 10–20 · Sections 2–3 · arXiv:2504.17555v2

Maximal independence makes every original sequence an integer combination of basis sequences modulo a term tending to zero. The induced map to a compact torus has kernel exactly the declared relation subgroup. Haar measure on the annihilator has Fourier transform equal to one on the kernel and zero off it; smoothing and pushforward produce the continuous measures needed for weak mixing without changing the selected limits.

Sections 4–5Correct and complete

Unitary/Gaussian realization and interpolation

Pages 20–29 · Sections 4–5 · arXiv:2504.17555v2

The spectral theorem represents the constructed Fourier coefficients as matrix coefficients of a unitary operator. The Gaussian construction turns that representation into a measure-preserving transformation, and atomlessness excludes eigenfunctions outside the constants. Rigidity follows by $L^2$ convergence on the first Gaussian chaos and then on the generated sigma-field. Mixing limits are first checked on Gaussian polynomials and extended by density, yielding Theorem 1.8.

03Novelty0 reported findingsNo non-novelty findings

No non-novelty findings.

Detailed audit reportFull reasoning, manuscript locations, and references.

Open report PDF ↗

Author response

Challenge an audit finding

Local workflow preview

A listed author may submit formal evidence that an audit is inaccurate. The response would be considered in a fresh AI re-evaluation; it would not edit the audit automatically.

Paper: arXiv:2504.17555v2
Authors listed: Rigoberto Zelada
Audit date: August 18, 2026

01Establish identityMatch an authenticated scholarly identity to this paper.
02Submit evidenceIdentify the finding and give a formal mathematical response.
03Re-evaluateA separate agent checks the response and records a disposition.

Email fallback for papers without a linked ORCID

A production fallback could send a one-time link only when the submitted address matches an independently maintained author-contact allowlist for this paper. MathAudit must return the same message for every address so the form cannot reveal which contacts are on that list.

Structured response preview

This form remains unavailable until production identity verification succeeds. Nothing entered here is submitted.

Audit finding challengedWhy the evaluation is inaccurateFormal evidence or repairVerifiable sources, if anyI am submitting evidence, not instructions for the reviewing agent.

This panel never establishes authorship in the local prototype. A production result should be described narrowly as an authenticated ORCID match or control of a separately allowlisted author-contact mailbox.

Audit controls

Status: Report ready
Source: arXiv v2
Prompt: Standard prompt · locked

The report is available below and in the public summary.

Review prompt

You are a mathematical auditor. Evaluate only the correctness of the paper's central statements, the correctness and completeness of its proofs, and evidence-backed non-novelty. Do not make editorial comments or evaluate importance, exposition, style, or suitability for publication. Keep the report neutral, precise, and professional. PART 1 — CORRECTNESS OF THE MAIN STATEMENTS Identify the paper's central statements and assess each one separately using exactly one of these outcomes: - Correct: the statement has a correct, verifiable proof; or, despite a defect in the printed proof, you can give a fully verified repair or independent proof. - Incorrect: you can give strong formal evidence that the statement as written is false, preferably a counterexample or a complete contradiction. - Not able to verify: the supplied proof does not establish the statement, and you can neither supply a fully verified proof nor disprove it. For every adverse or unverified outcome, restate the exact claim and hypotheses, identify its location in the reviewed version, and give the decisive reasoning. Do not infer that a theorem is false merely because its printed proof is defective. Assign the overall statements status by the following priority: 1. Contains wrong statements, if at least one central statement is Incorrect. 2. Contains unsupported statements, if no central statement is Incorrect but at least one is Not able to verify. 3. Correct, if every central statement is Correct, apart from any typographical or minor formal findings allowed by Part 4. PART 2 — CORRECTNESS AND COMPLETENESS OF THE PROOFS Audit the proofs of the central statements and every material internal or cited input on which they depend. For each proof or proof segment, use the narrowest supported outcome: - Correct and complete: every substantive step is verifiable and no case or crucial nontrivial step is missing. - Incorrect as written: a displayed calculation, inference, lemma, or cited application is formally false or inapplicable. - Incomplete as written: a necessary substantive step or case is missing, even though no explicit contradiction has been proved. - Not able to verify: the available paper and sources are insufficient to decide whether the step is valid. Do not flag omitted routine details, compressed arguments, or “analogously” steps when the omitted reasoning is recoverable and correct. For every defect, identify its smallest exact location, explain its downstream dependency, and classify any proposed repair as one of: - Verified repair: supply enough reasoning to verify that the repair works throughout every affected use. - Plausible repair only: describe the possible repair but do not treat it as established. - No repair supplied. Assign the overall proofs status by the following priority: 1. Contains incorrect or incomplete proofs, if at least one proof is Incorrect as written or Incomplete as written. 2. Contains unverified proofs, if there is no proved incorrectness or incompleteness but at least one material proof is Not able to verify. 3. Correct, if all audited proofs are Correct and complete, apart from any typographical or minor formal findings allowed by Part 4. PART 3 — NOVELTY OF THE MAIN STATEMENTS This is a one-sided, evidence-only check. Evaluate only central results. Report a result only when a verifiable primary source, publicly available before the earliest public version of the paper that contains the result, proves the same statement up to a change of notation, or when the result follows directly and immediately from such an earlier theorem. For each non-novelty finding, provide the earlier source, its public date, the exact theorem or proposition, and an explicit hypothesis-and-conclusion mapping. A later source cannot establish non-novelty. Do not flag a result merely because an easier proof exists or because it follows through a nontrivial argument. Do not flag a result that the paper itself explicitly presents as known, a survey item, or an alternative proof. Mention only statements that meet this non-novelty threshold. Say nothing about statements for which no such evidence was found: do not certify novelty, list unsuccessful searches, or add statement-level “no prior source found” entries. If the list is empty, the section may say only “No non-novelty findings.” PART 4 — TECHNICAL AND EVIDENTIARY RULES 1. Criticism must never be overstated. Call a statement incorrect, a proof incorrect or incomplete, or a result non-new only when strong formal evidence supports that exact judgment. Otherwise use Not able to verify where that outcome exists, or remain silent in the novelty section. 2. Review a specified paper version. Give exact page, theorem, equation, or proof locations; restate relevant quantifiers and hypotheses; and check domains, endpoints, parameter ranges, constants, and dependencies explicitly. Apply a defect only to the regimes and downstream results that actually depend on it. 3. Immediate-consequence closure: when deciding whether a conclusion is supported, treat the argument as including every immediate formal consequence of facts established earlier in the paper and available at that point. An immediate formal consequence is a local, mechanically checkable inference using only definitions already in force, elementary logic, direct substitution or renaming, weakening of an inequality or set inclusion, or a monotonicity or symmetry property explicit in a definition or already proved. 4. Such an inference must introduce no new lemma, estimate, construction, case analysis, limiting or compactness argument, external result, or new issue of uniformity or parameter dependence. Check the direction of monotonicity and the dependence of every threshold or constant explicitly. Do not exchange pointwise and uniform conclusions, change exceptional sets, interchange quantifiers or limits, or extend an endpoint under this rule unless the required fact was already established. 5. If the claimed conclusion follows after immediate-consequence closure, it is fully supported. Do not report a gap, unsupported statement, minor formal correction, or recommendation to add an explanatory sentence, and do not mention the suppressed item in the report. This suppression does not apply to a genuine typographical error as defined below, because a typo is a literal notation defect that still requires a textual correction. For example, if

P(delta)

is proved for every sufficiently small

delta>0

and

P

is immediately monotone in the required direction, then the claim that

P(delta)

holds for every

delta>0

requires no correction; the omitted monotonicity step is exposition rather than an audit finding. 6. Immediate-consequence closure permits reconstruction of an omitted inference; it does not permit silent alteration of the printed domain, hypotheses, or quantifiers of an intermediate statement later invoked outside its stated scope. If formal validity requires changing the text of that statement or its stated range, report the appropriate finding even when the repair is easy. Thus a result stated only for

t>0

and subsequently applied at

t=0

remains a formal scope mismatch unless the endpoint case was separately established before the application. 7. Apply this mandatory gate before recording any adverse, unverified, typographical, or minor formal finding: (a) identify the exact assertion or inference alleged to be defective; (b) reconstruct the strongest conclusion following from the preceding argument after all admissible immediate formal consequences are added; (c) identify the specific defect that remains — a formally demonstrated falsehood, a concrete nontrivial unresolved proof obligation, or a genuine domain, hypothesis, quantifier, or notation mismatch requiring a textual correction; and (d) state the evidence and minimal repair. If no specific defect remains, or if the only possible addition would be explanatory, suppress the finding entirely. Use Not able to verify only when a precise, nontrivial unresolved obligation can be identified. 8. A typographical error is an incorrect symbol, index, exponent, sign, variable name, or notation mismatch whose unique intended correction is mechanically determined from the surrounding text and does not alter the mathematical argument. Report it in yellow as Typo, with the printed text, correction, exact location, and reason it is harmless. It does not lower an overall status. 9. A minor formal correction is a boundary, endpoint, or displayed parameter-range defect that can be repaired consistently in every affected statement by a local change, without a new argument, without invalidating any related result or application, and without creating another substantive defect. Report it in yellow as Minor formal correction, with the same details. It does not lower an overall status. 10. Do not use either minor category if more than one materially different repair is possible; if the repair changes the substance or scope of a central result; if an excluded case is used later; if the correction fails to propagate consistently; or if a new mathematical idea is required. In such cases use the strongest substantive classification actually supported by evidence. 11. Write every mathematical expression as valid, compilable LaTeX. Use

...

for inline mathematics and

...

for displayed mathematics, with balanced delimiters and braces. Do not leave raw LaTeX commands outside math delimiters. 12. Separate theorem truth from the correctness of the printed proof. A theorem can be Correct in Part 1 because of a fully verified independent proof while its printed proof is adverse in Part 2. Conversely, a defective proof alone never licenses an Incorrect theorem classification. Organize the report under Parts 1–3 and apply Part 4 throughout. Do not add editorial commentary, scores, rankings, recommendations, or a list of suppressed observations.

This panel is visibly marked as owner-only for the concept prototype. Authentication is not enabled locally.

Coexistence of mixing and rigid behaviors in ergodic theory

Paper metadata

Abstract

Audit summary

Detailed mathematical audit

Equivalent characterizations of rigidity groups

Coexistence of prescribed mixing and rigidity

Passage from one realization to a residual class

Theorem 3.1 and the Gaussian realization

Asymptotic relations and Fourier limits

Unitary/Gaussian realization and interpolation

Challenge an audit finding

Authenticate with ORCID, then require an exact arXiv match