Proof of the singularity conjecture for discrete subgroups of $\mathrm{SL}_2(\mathbb{R})$

Timothée Bénard

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arXiv · 2609.17506

Proof of the singularity conjecture for discrete subgroups of $\mathrm{SL}_2(\mathbb{R})$

Timothée Bénard

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Abstract

Let $μ$ be a finitely supported probability measure on $\mathrm{SL}_2(\mathbb{R})$ whose support generates a Zariski-dense discrete subgroup. We prove that its stationary probability measure on $\mathbb{P}^1(\mathbb{R})$ is singular with respect to the $\mathrm{SO}(2)$-invariant probability measure. The proof compares winding variances on finite covers of a closed hyperbolic surface and uses a topological obstruction.

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Timothée Bénard. 2026-09-15. Proof of the singularity conjecture for discrete subgroups of $\mathrm{SL}_2(\mathbb{R})$. https://arxiv.org/abs/2609.17506

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