Continuity conjecture for the Hausdorff dimension of branching-random-walk limit sets

Consider a branching random walk (BRW) on a non-amenable Cayley graph. Let PP be the transition kernel of the underlying random walk, let ρ(P)\rho(P) be its spectral radius, let mm be the mean offspring number, and let the limit set be the random subset of the geometric boundary consisting of ends visited infinitely often by the BRW.

Hausdorff-dimension continuity conjecture. The Hausdorff dimension of the limit set is continuous for m1/ρ(P)m\neq 1/\rho(P) and discontinuous at m=1/ρ(P)m=1/\rho(P).

For m>1/ρ(P)m>1/\rho(P) the BRW is recurrent and the limit set equals the full boundary. The source relates the conjecture to known results for homogeneous trees, but the stated general claim remains open.

Sources & referencesView supporting material

Primary source

Itai Benjamini and Sebastian Müller, “On the trace of branching random walks”, arXiv:1002.2781 (2010).

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