Abstract
M. Gromov has shown that any two finitely generated groups \(\Gamma \) and \(\Lambda \) are quasi-isometric if and only if they admit a topological coupling, i.e., a commuting pair of proper continuous cocompact actions \(\Gamma \curvearrowright X \curvearrowleft \Lambda \) on a locally compact Hausdorff space. This result is extended here to all (compactly generated) locally compact second-countable groups.
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The G-action written on the left will be a left-action, while the H-action written on the right will be a right-action. However, both groups G and H will be equipped with their left-invariant coarse structure, which is that induced by a compatible proper left-invariant metric.
References
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U. B. was partially supported by the ISF-Moked Grant 2095/15 and the ERC Grant 306706, C. R. was partially supported by the NSF (DMS 1464974). The authors are grateful for the helpful suggestions by the referee.
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Bader, U., Rosendal, C. Coarse equivalence and topological couplings of locally compact groups. Geom Dedicata 196, 1–9 (2018). https://doi.org/10.1007/s10711-017-0300-7
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DOI: https://doi.org/10.1007/s10711-017-0300-7