Abstract
We prove uniform Ancona—Gouëzel—Lalley inequalities for an extension by a hyperbolic group G of a Markov map which allows to deduce that the visual boundary of the group and the Martin boundary are Hölder equivalent. As application, we identify the set of minimal δ-conformal measures of a regular cover of a convex-cocompact CAT(-1)-manifold with the visual boundary of the covering group, provided that this group is hyperbolic. In this setting, the uniformity allows to identify the visual boundary with minimal, δ-conformal densities in the sense of Patterson with respect to the exponent of convergence δ. This is of interest as δ coincides with the Hausdorff dimension of the radial limit set. Moreover, this extends Roblin’s identification of s-conformal densities for s > δ.
We’re sorry, something doesn't seem to be working properly.
Please try refreshing the page. If that doesn't work, please contact support so we can address the problem.
References
J. Aaronson, An Introduction to Infinite Ergodic Theory, Mathematical Surveys and Monographs, Vol. 50, American Mathematical Society, Providence, RI, 1997.
J. Aaronson, M. Denker and M. Urbański, Ergodic theory for Markov fibred systems and parabolic rational maps, Transactions of the American Mathematical Society 337 (1993), 495–548.
T. Adachi, Markov families for anosov flows with an involutive action, Nagoya Mathematical Journal 104 (1986), 55–62.
A. Ancona, Negatively curved manifolds, elliptic operators, and the Martin boundary, Annals of Mathematics 125 (1987), 495–536.
J. W. Anderson, K. Falk and P. Tukia, Conformal measures associated to ends of hyperbolic n-manifolds, Quarterly Journal of Mathematics 58 (2007), 1–15.
C. J. Bishop and P. W. Jones, Hausdorff dimension and Kleinian groups, Acta Mathematica 179 (1997), 1–39.
R. Brooks, The bottom of the spectrum of a Riemannian covering, Journal für die Reine und Angewandte Mathematik 357 (1985), 101–114.
P.-E. Caprace, Y. Cornulier, N. Monod and R. Tessera, Amenable hyperbolic groups, Journal of the European Mathematical Society 17 (2015), 2903–2947.
D. Constantine, J.-F. Lafont and D. J. Thompson, Strong symbolic dynamics for geodesic flow on CAT(−1) spaces and other metric Anosov flows, Journal de l’École polytechnique. Mathématiques 7 (2020), 201–231.
M. Coornaert and A. Papadopoulos, Horofunctions and symbolic dynamics on Gromov hyperbolic groups, Glasgow Mathematical Journal 43 (2001), 425–456.
R. Coulon, F. Dal’Bo and A. Sambusetti, Growth gap in hyperbolic groups and amenability, Geometric and Functional Analysis 28 (2018), 1260–1320.
T. Das, D. Simmons and M. Urbański, Geometry and Dynamics in Gromov Hyperbolic Metric Spaces: With an Emphasis on Non-Proper Settings, Mathematical Surveys and Monographs, Vol. 218, American Mathematical Society, Providence, RI, 2017.
R. Dougall and R. Sharp, Amenability, critical exponents of subgroups and growth of closed geodesics, Mathematische Annalen 365 (2016), 1359–1377.
K. Falk, K. Matsuzaki and B. O. Stratmann, Checking atomicity of conformal ending measures for kleinian groups, Conformal Geometry and Dynamics 14 (2010), 167–183.
E. Ghys and P. de la Harpe, Espaces métriques hyperboliques, in Sur les Groupes Hyperboliques d’après Mikhael Gromov, Progress in Mathematics, Vol. 83, Birkhäuser, Basel, 1990, pp. 27–46.
E. Ghys and P. de la Harpe, Le bord d’un espace hyperbolique, in Sur les Groupes Hyperboliques d’après Mikhael Gromov, Progress in Mathematics, Vol. 83, Birkhäuser, Basel, 1990, pp. 117–134.
S. Gouëezel, Local limit theorem for symmetric random walks in Gromov-hyperbolic groups, Journal of the American Mathematical Society 27 (2014), 893–928.
S. Gouëzel, Martin boundary of random walks with unbounded jumps in hyperbolic groups, Annals of Probability 43 (2015), 2374–2404.
S. Gouëzel and S. P. Lalley, Random walks on co-compact Fuchsian groups, Annales Scientifiques de l’École Normale Supérieure 46 (2013), 129–173.
M. Gromov, Hyperbolic groups, in Essays in Group Theory, Mathematical Sciences Research Institute Publications, Vol. 8, Springer, New York, 1987, pp. 75–263.
J. Jaerisch, Recurrence and pressure for group extensions, Ergodic Theory and Dynamical Systems 26 (2016), 108–126.
V. A. Kaimanovich, Ergodic properties of the horocycle flow and classification of Fuchsian groups, Journal of Dynamical and Control Systems 6 (2000), 21–56.
A. Karlsson and G. A. Margulis, A multiplicative ergodic theorem and nonpositively curved spaces, Communications in Mathematical Physics 208 (1999), 107–123.
H. Kesten, Full Banach mean values on countable groups, Mathematica Scandinavica 7 (1959), 146–156.
R. S. Martin, Minimal positive harmonic functions, Transactions of the American Mathematical Society 49 (1941), 137–172.
M. Murata, Martin boundaries of elliptic skew products, semismall perturbations, and fundamental solutions of parabolic equations, Journal of Functional Analysis 194 (2002), 53–141.
M. Rees, Checking ergodicity of some geodesic flows with infinite Gibbs measure, Ergodic Theory and Dynamical Systems 1 (1981), 107–133.
D. Revuz, Markov chains, North-Holland Mathematical Library, Vol. 11, North-Holland, Amsterdam, 1984.
T. Roblin, Ergodicité et équidistribution en courbure négative, Mémoires de la Société Mathematique de France 95 (2003).
T. Roblin, Comportement harmonique des densités conformes et frontière de Martin, Bulletin de la Société Mathématique de France 139 (2011), 97–128.
O. M. Sarig, Existence of Gibbs measures for countable Markov shifts, Proceedings of the American Mathematical Society 131 (2003), 1751–1758.
O. Shwartz, Thermodynamic formalism for transient potential functions, Communications in Mathematical Physics 366 (2019), 737–779.
O. Shwartz, The conformal measures of a normal subgroup of a cocompact Fuchsian group, Ergodic Theory and Dynamical Systems 41 (2021), 2845–2878.
M. Stadlbauer, An extension of Kesten’s criterion for amenability to topological Markov chains, Advances in Mathematics 235 (2013), 450–468.
M. Stadlbauer, On conformal measures and harmonic functions for group extensions, in New Trends in One-Dimensional Dynamics, Springer Proceedings in Mathematics & Statistics, Vol. 285, Springer, Cham, 2019, pp. 271–299.
W. Woess, Random walks on infinite graphs and groups—a survey on selected topics, Bulletin of the London Mathematical Society 26 (1994), 1–60.
W. Woess, Denumerable Markov chains, EMS Textbooks in Mathematics, European Mathematical Society, Zürich, 2009.
R. J. Zimmer, Amenable ergodic group actions and an application to Poisson boundaries of random walks, Journal of Functional Analysis 27 (1978), 350–372.
Acknowledgements
The authors would like to express their deep gratitude for support of the Post-Graduate program of the Universidade Federal da Bahia, where the first author obtained her PhD in 2019 under the supervision of the second author. In particular, the authors acknowledge support by CAPES and CNPq: The first author was supported by CAPES during her PhD studies, and the second author was partially supported by CAPES (Programa PROEX da Pós-Graduação em Matemática do IM-UFRJ) and CNPq (PQ 312632/2018-5, Universal 426814/2016-9).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Bispo, S.R.P., Stadlbauer, M. The Martin boundary of an extension by a hyperbolic group. Isr. J. Math. 255, 1–62 (2023). https://doi.org/10.1007/s11856-023-2468-x
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11856-023-2468-x