Connectivity of Markoff and Nielsen graphs

By Daniel Martin

Appears in collection : 2026 - T1 - WS3 - Integrating Research and Illustration in Number Theory

The generalized Markoff equation gives rise to a dynamical system via the Markoff group action on its solution set. Over finite fields, the action produces graphs that are conjectured by Bourgain, Gamburd, and Sarnak to form an expander family. This conjecture has implications in both number theory (strengthening the affine linear sieve for Markoff numbers) and computational group theory (bounding runtime of the Product Replacement Algorithm for $SL_2(F_p)$). In this talk, we discuss recent progress toward proving connectivity of Markoff graphs and related results on Nielsen graphs of matrix pairs from $SL_2(F_p)$.

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Citation data

  • DOI 10.57987/IHP.2026.T1.WS3.007
  • Cite this video Martin, Daniel (24/03/2026). Connectivity of Markoff and Nielsen graphs. IHP. Audiovisual resource. DOI: 10.57987/IHP.2026.T1.WS3.007
  • URL https://dx.doi.org/10.57987/IHP.2026.T1.WS3.007

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Bibliography

  • Jean Bourgain, Alex Gamburd, and Peter Sarnak. Affine linear sieve, expanders, and sum-product. Inventiones Mathematicae, 179(3):559--644, 2010.
  • Jean Bourgain, Alex Gamburd, and Peter Sarnak. Markoff triples and strong approximation. Journal of the American Mathematical Society, 39(1):177--204, 2026.
  • Daniel Martin. Markoff triples and Nielsen equivalence in SL_2(F_p). arXiv:2510.07577, 2025.
  • Darryl McCullough and Marcus Wanderley. Nielsen equivalence of generating pairs of SL(2,q). Glasgow Mathematical Journal, 55(3):481--509, 2013.

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