Abstract

We establish a link between qq-deformed rational numbers and the classical Burau representation of the braid group B3B_3. This gives a classification of faithful complex specializations in terms of the singular set of the qq-rationals and proves faithfulness outside the annulus 3−22≤∣t∣≤3+223-2\sqrt{2}\le |t|\le3+2\sqrt{2}.

Role in dependence graphs

Proof-critical source

On qq-real and qq-complex numbers

This paper is included only for the following marked statement:

  • Theorem 1 · IMRN 2024 VOR pp. 8620-8624Equates a zero of a qq-rational numerator polynomial with nonfaithfulness of the specialized reduced Burau representation.

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Open repository version of record · International Mathematics Research Notices 2024, no. 10, 8618–8627

Sophie Morier-Genoud, Valentin Ovsienko, and Alexander P. Veselov. Burau representation of braid groups and qq-rationals. International Mathematics Research Notices 2024, no. 10, 8618–8627.

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Generated August 27, 2026
01Statements2 reported findingsNo statement issues found

The singular-set characterization of nonfaithful specializations of the reduced Burau representation of B3B_3 and the resulting faithfulness region outside 3−22≤∣t∣≤3+223-2\sqrt{2}\le |t|\le3+2\sqrt{2} are correctly stated. The root condition is attached to the numerator polynomials of qq-rationals with the reciprocal and sign conventions needed for the specialization.

Theorem 1No issue found

Polynomial zeros and Burau nonfaithfulness are equivalent

Printed pages 8620–8624 · version of record

The projectivized Burau action is identified with the qq-deformed modular action. A nontrivial kernel word fixes the associated rational point, giving a numerator zero; conversely, a numerator zero makes two distinct modular words have the same specialized projective action. The scalar ambiguity is removed by the determinant/central-element calculation, so the conclusion concerns the linear Burau representation rather than only its projectivization.

IMRN version of record ↗
Theorem 2No issue found

The annular faithfulness bound follows with reciprocal endpoints

Printed pages 8624–8626 · version of record

The numerator and denominator polynomials have reciprocal root symmetry, while the elementary coefficient bound excludes roots in the inner disk. Applying the symmetry excludes the exterior reciprocal disk, producing exactly the displayed annulus.

02Proofs2 reported findingsNo proof issues found

The modular-action identification, free-subgroup argument, scalar lift, and reciprocal-root estimate close the two main proofs. The proof-critical use of the Kurosh subgroup theorem is represented by a terminal book source, and the needed qq-rational facts are verified in the exact MO1 version of record.

Proof of Theorem 1No issue found in the reviewed proof

The free-subgroup and projective-lift steps rule out both directions of failure

Printed pages 8621–8624 · version of record

The relevant subgroup of the modular/free-product presentation is free by the Kurosh theorem. The qq-rational orbit map records its reduced words, so equality of specialized orbit values yields precisely a projective kernel relation. Tracking determinants and the image of the center then lifts the relation to the reduced Burau representation with no missing exceptional scalar case.

IMRN version of record ↗
Proof of Theorem 2No issue found in the reviewed proof

The zero-free disk and reciprocity arguments are compatible

Printed pages 8624–8626 · version of record

Positivity of the qq-rational coefficients gives the uniform inner zero-free estimate. The involution on continued fractions exchanges numerator and denominator with the reciprocal-polynomial transformation, so every exterior root would produce a prohibited inner root. The endpoint arithmetic simplifies to 3±223\pm2\sqrt{2} as printed.

03Novelty0 reported findingsNo novelty concerns found

No non-novelty findings.

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