English

Markoff triples and Nielsen equivalence in $\text{SL}_2(\mathbb{F}_p)$

Number Theory 2025-11-24 v2

Abstract

In 2013, Darryl McCullough and Marcus Wanderley made a series of conjectures that describe the Nielsen equivalence classes and T2T_2-equivalence classes of pairs of generators for SL2(Fq)\text{SL}_2(\mathbb{F}_q) and the Markoff equivalence classes of triples in Fq3\mathbb{F}_q^3 that solve x2+y2+z2=xyz+κx^2+y^2+z^2=xyz+\kappa for some κFq\kappa\in\mathbb{F}_q. (The case κ=0\kappa=0 was originally conjectured by Baragar in 1991.) We prove that one of the McCullough-Wanderley conjectures, the "Q-Classification Conjecture" on Markoff triples, implies the others. Then we prove that the Q-Classification Conjecture holds if q=pq=p is a prime such that 24,504,48024{,}504{,}480 does not divide p21p^2-1. More generally, for any integer dd, we reduce the Q-Classification Conjecture for all primes p≢±1moddp\not\equiv \pm 1\,\text{mod}\,d to checking whether a roughly 2d×2d2d\times 2d matrix with entries in Q[κ]\mathbb{Q}[\kappa] is invertible. We (and SageMath) perform this invertibility check for all prime powers dd up to 1717, hence the modulus 24,504,480=2lcm(1,2,,17)24{,}504{,}480=2\text{lcm}(1,2,\dots,17).

Keywords

Cite

@article{arxiv.2510.07577,
  title  = {Markoff triples and Nielsen equivalence in $\text{SL}_2(\mathbb{F}_p)$},
  author = {Daniel E. Martin},
  journal= {arXiv preprint arXiv:2510.07577},
  year   = {2025}
}

Comments

62 pages. Typos from version 1 have been fixed, and further explanation has been added to certain proofs. Sage code for Algorithm 1 is on the author's webpage: dem6.people.clemson.edu