Abstract
We prove that, if a topological group G has an open subgroup of infinite index, then every net of tight Borel probability measures on G UEB-converging to invariance dissipates in G in the sense of Gromov. In particular, this solves a 2006 problem by Pestov: for every left-invariant (or right-invariant) metric d on the infinite symmetric group Sym(ℕ), compatible with the topology of pointwise convergence, the sequence of the finite symmetric groups (Sym(n), d ↾Sym(n), μSym(n))n∈ℕ equipped with the restricted metrics and their normalized counting measures dissipates, thus fails to admit a subsequence being Cauchy with respect to Gromov’s observable distance.
Similar content being viewed by others
References
A. Arhangel’skii and M. Tkachenko, Topological Groups and Related Structures, Atlantis Studies in Mathematics, Vol. 1, Atlantis Press, Paris; World Scientific Publishing, Hackensack, NJ, 2008.
V. I. Bogachev, Measure Theory. Vol. I, Springer, Berlin, 2007.
A. Bouziad and J.-P. Troallic, A precompactness test for topological groups in the manner of Grothendieck, Topology Proceedings 31 (2007), 19–30.
V. V. Buldygin and A. B. Kharazishvili, Geometric Aspects of Probability Theory and Mathematical Statistics, Mathematics and its Applications, Vol. 514, Kluwer Academic, Dordrecht, 2000.
D. Burago, Y. Burago and S. Ivanov, A Course in Metric Geometry, Graduate Studies in Mathematics, Vol. 33, American Mathematical Society, Providence, RI, 2001.
T. Giordano and V. G. Pestov, Some extremely amenable groups related to operator algebras and ergodic theory, Journal of the Institute of Mathematics of Jussieu 6 (2007), 279–315.
E. Glasner, B. Tsirelson and B. Weiss, The automorphism group of the Gaussian measure cannot act pointwise, Israel Journal of Mathematics 148 (2005), 305–329.
E. Glasner and B. Weiss, Minimal actions of the group S(Z) of permutations of the integers, Geometric and Functional Analysis 12 (2002), 964–988.
M. Gromov, Metric Structures for Riemannian and Non-Riemannian Spaces, Progress in Mathematics, Vol. 152, Birkhäuser Boston, Boston, MA, 1999.
M. Gromov and V. D. Milman, A topological application of the isoperimetric inequality, American Journal of Mathematics 105 (1983), 843–854.
P. Holm, On the Bohr compactißcation, Mathematische Annalen 156 (1964), 34–46.
J. L. Kelley, General Topology, Graduate Texts in Mathematics, Vol. 27, Springer, New York, 1975.
M. Ledoux, The concentration of measure phenomenon, Mathematical Surveys and Monographs, Vol. 89, American Mathematical Society, Providence, RI, 2001.
P. Lévy, Leçons d’analyse fonctionnelle, Gauthier-Villars, Paris, 1922.
B. Maurey, Constructions de suites symétriques, Comptes Rendus de l’Academie des Sciences. Série A-B 288 (1979), 679–681.
V. D. Milman, Infinite-dimensional geometry of the unit sphere in Banach space, Soviet Mathematics. Doklady 8 (1967), 1440–1444.
V. D. Milman and G. Schechtman, Asymptotic Theory of Finite Dimensional Normed Spaces, Lecture Notes in Mathematics, Vol. 1200, Springer, Berlin-Heidelberg, 1986.
J. Pachl, Uniform Spaces and Measures, Fields Institute Monographs, Vol. 30, Springer, New York; Fields Institute for Research in Mathematical Sciences, Toronto, ON, 2013.
K. R. Parthasarathy, Probability Measures on Metric Spaces, Probability and Mathematical Statistics, Vol. 3, Academic Press, New York-London, 1967.
V. G. Pestov, Ramsey-Milman phenomenon, Urysohn metric spaces, and extremely amenable groups, Israel Journal of Mathematics 127 (2002), 317–357.
V. G. Pestov, Dynamics of Infinite-Dimensional Groups: The Ramsey-Dvoretzky-Milman Phenomenon, University Lecture Series, Vol. 40, American Mathematical Society, Providence, RI, 2006.
V. G. Pestov, Concentration of measure and whirly actions of Polish groups, in Probabilistic Approach to Geometry, Advanced Studied in Pure Mathematics, Vol. 57, Mathematical Society of Japan, Tokyo, 2010, pp. 383–403.
V. G. Pestov and F. M. Schneider, On amenability and groups of measurable maps, Journal of Functional Analysis 273 (2017), 3859–3874.
F. M. Schneider, Equivariant concentration in topological groups, Geometry & Topology 23 (2019), 925–956.
F. M. Schneider and A. Thom, On Følner sets in topological groups, Compositio Mathematica 154 (2018), 1333–1362.
T. Shioya, Metric Measure Geometry, IRMA Lectures in Mathematics and Theoretical Physics, Vol. 25, EMS Publishing House, Zürich, 2016.
S. Solecki, Actions of non-compact and non-locally compact Polish groups, Journal of Symbolic Logic 65 (2000), 1881–1894.
V. V. Uspenskij, On subgroups of minimal topological groups, Topology and its Applications 155 (2008), 1580–1606.
J. de Vries, Elements of Topological Dynamics, Mathematics and Its Applications, Vol. 257, Kluwer Academic, Dordrecht, 1993.
Acknowledgments
This research has been supported by funding of the Excellence Initiative by the German Federal and State Governments as well as the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), processo 150929/2017-0. The author is deeply indebted to Vladimir Pestov for a number of inspiring and insightful discussions about the concentration of measured metric spaces, as well as to Tom Hanika for a helpful exchange on combinatorics of finite permutation groups. Also, the kind hospitality of CFM-UFSC (Florianópolis) during the origination of this work is gratefully acknowledged. Furthermore, the author would like to express his sincere gratitude towards the anonymous referee for their careful reading and valuable remarks, including a substantial simplification of an earlier proof of Theorem 5.1!
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Schneider, F.M. Equivariant dissipation in non-archimedean groups. Isr. J. Math. 234, 281–307 (2019). https://doi.org/10.1007/s11856-019-1927-x
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11856-019-1927-x