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arXiv · 1706.06712

Integral points on Markoff type cubic surfaces

Amit Ghosh·Peter Sarnak
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Abstract

For integers $k$, we consider the affine cubic surface $V_{k}$ given by $M({\bf x})=x_{1}^2 + x_{2}^2 +x_{3}^2 -x_{1}x_{2}x_{3}=k$. We show that for almost all $k$ the Hasse Principle holds, namely that $V_{k}(\mathbb{Z})$ is non-empty if $V_{k}(\mathbb{Z}_p)$ is non-empty for all primes $p$, and that there are infinitely many $k$'s for which it fails. The Markoff morphisms act on $V_{k}(\mathbb{Z})$ with finitely many orbits and a numerical study points to some basic conjectures about these "class numbers" and Hasse failures. Some of the analysis may be extended to less special affine cubic surfaces.

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Amit Ghosh, Peter Sarnak. 2017-06-21. Integral points on Markoff type cubic surfaces. https://doi.org/10.1007/s00222-022-01114-z

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