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Sierpiński gasket as a Martin boundary. II: The intrinsic metric. (English) Zbl 0980.60095

Authors’ summary: It is shown in part I (reviewed above) that the Sierpiński gasket \({\mathcal S}\subset \mathbb{R}^N\) can be represented as the Martin boundary of a certain Markov chain and hence carries a canonical metric \(\rho_M\) induced by the embedding into an associated Martin space \(M\). It is a natural question to compare this metric \(\rho_M\) with the Euclidean metric. We show first that the harmonic measure coincides with the normalized \(H=(\log (N+1)/\log 2)\)-dimensionaI Hausdorff measure with respect to the Euclidean metric. Secondly, we define an intrinsic metric \(\rho\) which is Lipschitz equivalent to \(\rho_M\) and then show that \(\rho\) is not Lipschitz equivalent to the Euclidean metric, but the Hausdorff dimension remains unchanged and the Hausdorff measure in \(\rho\) is infinite. Finally, using the metric \(\rho\), we prove that the harmonic extension of a continuous boundary function converges to the boundary value at every boundary point.
Reviewer: Uwe Rösler (Kiel)

MSC:

60J10 Markov chains (discrete-time Markov processes on discrete state spaces)
60J50 Boundary theory for Markov processes
31C05 Harmonic, subharmonic, superharmonic functions on other spaces

Citations:

Zbl 0980.60094
Full Text: DOI

References:

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