Besov spaces and random walks on a hyperbolic group: boundary traces and reflecting extensions of Dirichlet forms
Annales Henri Lebesgue, Volume 7 (2024), pp. 161-206.

Metadata

Keywords Random walks, Dirichlet forms, Besov spaces, hyperbolic groups, local times

Abstract

We show the existence of a trace process at infinity for random walks on hyperbolic groups of conformal dimension <2 and relate it to the existence of a reflected random walk. To do so, we employ the theory of Dirichlet forms which connects the theory of symmetric Markov processes to functional analytic perspectives. We introduce a family of Besov spaces associated to random walks and prove that they are isomorphic to some of the Besov spaces constructed from the co-homology of the group studied in Bourdon–Pajot (2003). We also study the regularity of harmonic measures of random walks on hyperbolic groups using the potential theory associated to Dirichlet forms.


References

[BH99] Bridson, M.; Haefliger, A. Metric spaces of non-positive curvature, Grundlehren der Mathematischen Wissenschaften, 319, Springer, 1999 | DOI | Zbl

[BHM11] Blachère, S.; Haïssinsky, P.; Mathieu, P. Harmonic measures versus quasiconformal measures for hyperbolic groups, Ann. Sci. Éc. Norm. Supér., Volume 44 (2011) no. 4, pp. 683-721 | DOI | Numdam | MR | Zbl

[BP03] Bourdon, M.; Pajot, H. Cohomologie p et espaces de Besov, J. Reine Angew. Math., Volume 558 (2003), pp. 85-108 | MR | Zbl

[Bur87] Burdzy, K. Multidimensional Brownian excursions and potential theory, Pitman Research Notes in Mathematics Series, 164, John Wiley & Sons, 1987 | Zbl

[CF12] Chen, Z.-Q.; Fukushima, M. Symmetric Markov processes, Time Change, and Boundary theory, London Mathematical Society Monographs, 35, Princeton University Press, 2012 | Zbl

[Che92] Chen, Z.-Q. On reflected Dirichlet spaces, Probab. Theory Relat. Fields, Volume 94 (1992) no. 2, pp. 135-162 | DOI | MR | Zbl

[CK08] Chen, Z.-Q.; Kumagai, T. Heat kernel estimates for jump processes of mixed types on metric measure spaces, Probab. Theory Relat. Fields, Volume 140 (2008) no. 1-2, pp. 277-317 | DOI | MR | Zbl

[CKW21] Chen, Z.-Q.; Kumagai, T.; Wang, J. Stability of heat kernel estimates for symmetric jump processes on metric measure spaces, Memoirs of the American Mathematical Society, 1330, American Mathematical Society, 2021 | Zbl

[Coo93] Coornaert, M. Mesures de Patterson–Sullivan sur le bord d’un espace hyperbolique au sens de Gromov, Pac. J. Math., Volume 159 (1993) no. 2, pp. 241-270 | DOI | MR | Zbl

[Cos09] Costea, Ş. Besov capacity and Hausdorff measures in metric measure spaces, Publ. Mat., Barc., Volume 53 (2009) no. 1, pp. 141-178 | DOI | MR | Zbl

[Dyn69] Dynkin, E. B. Boundary theory of Markov processes (the discrete case), Russ. Math. Surv., Volume 24 (1969) no. 2, pp. 1-42 | DOI | Zbl

[FOT11] Fukushima, M.; Oshima, Y.; Takeda, M. Dirichlet Forms and Symmetric Markov Processes, De Gruyter Studies in Mathematics, 19, Walter de Gruyter, 2011 | Zbl

[GdlH90] Ghys, E.; de la Harpe, P. Le bord d’un espace hyperbolique, Sur les groupes hyperboliques d’après Mikhael Gromov (Bern, 1988) (Progress in Mathematics), Volume 83, Birkhäuser, 1990, pp. 117-134 | DOI | MR

[GHH18] Grigor’yan, A.; Hu, E.; Hu, J. Two-sided estimates of heat kernels of jump type Dirichlet forms, Adv. Math., Volume 330 (2018), pp. 433-515 | DOI | MR | Zbl

[Gou15] Gouëzel, S. Martin boundary of random walks with unbounded jumps in hyperbolic groups, Ann. Probab., Volume 43 (2015) no. 5, pp. 2374-2404 | DOI | MR | Zbl

[Gro87] Gromov, M. Hyperbolic groups, Essays in group theory (Mathematical Sciences Research Institute Publications), Volume 8, Springer, 1987, pp. 75-263 | DOI | MR | Zbl

[Haï07] Haïssinsky, P. Géométrie quasiconforme, analyse au bord des espaces métriques hyperboliques et rigidités, Astérisque, 326, Société Mathématique de France, 2007, pp. 321-362 | Zbl

[Haï15] Haïssinsky, P. Hyperbolic groups with planar boundaries, Invent. Math., Volume 201 (2015) no. 1, pp. 239-307 | DOI | MR | Zbl

[Hei01] Heinonen, J. Lectures on Analysis on Metric Spaces, Universitext, Springer, 2001 | DOI | Numdam | Zbl

[Kai00] Kaimanovich, V. A. The Poisson formula for groups with hyperbolic properties, Ann. Math., Volume 152 (2000) no. 3, pp. 659-692 | DOI | MR | Zbl

[Kig10] Kigami, J. Dirichlet forms and associated heat kernels on the Cantor set induced by random walks on trees, Adv. Math., Volume 225 (2010) no. 5, pp. 2674-2730 | DOI | MR | Zbl

[LP16] Lyons, R.; Peres, Y. Probability on Trees and Networks, Cambridge Series in Statistical and Probabilistic Mathematics, 42, Cambridge University Press, 2016 | DOI | Zbl

[MS20] Mathieu, P.; Sisto, A. Deviation inequalities and CLT for random walks on acylindrically hyperbolic groups, Duke Math. J., Volume 169 (2020) no. 5, pp. 961-1036 | DOI | Zbl

[Naï57] Naïm, L. Sur le rôle de la frontière de R. S. Martin dans la théorie du potentiel, Ann. Inst. Fourier, Volume 7 (1957), pp. 183-281 | DOI | Numdam | MR | Zbl

[Par67] Parthasarathy, K. R. Probability measures on metric spaces, Probability and Mathematical Statistics: A Series of Monographs and Textbooks, 3, Academic Press Inc., 1967 | Zbl

[PS17] Piiroinen, P.; Simon, M. Probabilistic interpretation of the Calderón problem, Inverse Probl. Imaging, Volume 11 (2017) no. 3, pp. 553-575 | DOI | Zbl

[PSC00] Pittet, C.; Saloff-Coste, L. On the stability of the behavior of random walks on groups, J. Geom. Anal., Volume 10 (2000) no. 4, pp. 713-737 | DOI | MR | Zbl

[Sil74] Silverstein, M. L. Classification of stable symmetric Markov chains, Indiana J. Math., Volume 24 (1974), pp. 29-77 | DOI | MR | Zbl

[Soa94] Soardi, P. M. Potential theory on infinite networks, Lecture Notes in Mathematics, 1590, Springer, 1994 | DOI | Zbl

[Tan19] Tanaka, R. Dimension of harmonic measures in hyperbolic spaces, Ergodic Theory Dyn. Syst., Volume 39 (2019) no. 2, pp. 474-499 | DOI | MR | Zbl

[Woe00] Woess, W. Random Walks on Infinite Graphs and Groups, Cambridge Tracts in Mathematics, 138, Cambridge University Press, 2000 | DOI | Zbl