Divergence, undistortion and Hölder continuous cocycle superrigidity for full shifts

• Published in: Ergodic theory and dynamical systems 2021-08, Vol.41 (8), p.2274-2293
• Main Authors: CHUNG, NHAN-PHU, JIANG, YONGLE
• Format: Article
• Language: English
• Subjects: Cones; Homomorphisms; Lattices (mathematics); Lie groups; Metric space; Original Article; Punches; Topology
• ISSN: 0143-3857; 1469-4417
• DOI: 10.1017/etds.2020.44

In this article, we will prove a full topological version of Popa’s measurable cocycle superrigidity theorem for full shifts [Popa, Cocycle and orbit equivalence superrigidity for malleable actions of $w$ -rigid groups. Invent. Math. 170(2) (2007), 243–295]. Let $G$ be a finitely generated group that has one end, undistorted elements and sub-exponential divergence function. Let $H$ be a target group that is complete and admits a compatible bi-invariant metric. Then, every Hölder continuous cocycle for the full shifts of $G$ with value in $H$ is cohomologous to a group homomorphism via a Hölder continuous transfer map. Using the ideas of Behrstock, Druţu, Mosher, Mozes and Sapir [Divergence, thick groups, and short conjugators. Illinois J. Math. 58(4) (2014), 939–980; Thick metric spaces, relative hyperbolicity, and quasi-isometric rigidity. Math. Ann. 344(3) (2009), 543–595; Divergence in lattices in semisimple Lie groups and graphs of groups. Trans. Amer. Math. Soc. 362(5) (2010), 2451–2505; Tree-graded spaces and asymptotic cones of groups. Topology 44(5) (2005), 959–1058], we show that the class of our acting groups is large including wide groups having undistorted elements and one-ended groups with strong thick of finite orders. As a consequence, irreducible uniform lattices of most of higher rank connected semisimple Lie groups, mapping class groups of $g$ -genus surfaces with $p$ -punches, $g\geq 2,p\geq 0$ ; Richard Thompson groups $F,T,V$ ; $\text{Aut}(F_{n})$ , $\text{Out}(F_{n})$ , $n\geq 3$ ; certain (two-dimensional) Coxeter groups; and one-ended right-angled Artin groups are in our class. This partially extends the main result in Chung and Jiang [Continuous cocycle superrigidity for shifts and groups with one end. Math. Ann. 368(3–4) (2017), 1109–1132].