Kaimanovich–Masur singularity conjecture for mapping class groups

Let Σ\Sigma be a closed connected orientable surface of genus at least two, let Γ<Mod(Σ)\Gamma<\operatorname{Mod}(\Sigma) be a non-elementary subgroup, and let m\mathsf{m} be a probability measure on Γ\Gamma whose support generates Γ\Gamma as a semigroup. Let ν\nu be the unique m\mathsf{m}-stationary measure on Thurston's boundary PMF\mathcal{PMF}.

Kaimanovich–Masur singularity conjecture. If m\mathsf{m} has finite support, then the m\mathsf{m}-stationary measure ν\nu is singular to every Busemann Patterson–Sullivan measure for Γ\Gamma.

This conjecture concerns the relationship between random-walk hitting measures and geometric Patterson–Sullivan measures on the Thurston boundary. The source presents it as a conjecture suggested by Kaimanovich–Masur; its resolution status is not specified.

Sources & referencesView supporting material

Primary source

Dongryul M. Kim and Andrew Zimmer, “Rigidity for Patterson–Sullivan systems with applications to random walks and entropy rigidity”, arXiv:2505.16556 (2026).

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