Abstract
We show that if A is a closed subset of the Heisenberg group whose vertical projections are nowhere dense, then the complement of A is quasiconvex. In particular, closed sets which are null sets for the cc-Hausdorff 3-measure have quasiconvex complements. Conversely, we exhibit a compact totally disconnected set of Hausdorff dimension three whose complement is not quasiconvex.
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Acknowledgements
Research for this paper was conducted during visits of various subsets of the authors to the University of Illinois and the University of Cincinnati. The hospitality of these institutions is appreciated.
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Dedicated to William Goldman on the occasion of his 60th birthday.
J. T. T. was supported by Simons Foundation Collaboration Grant 353627 ‘Geometric Analysis in Sub-Riemannian and Metric Spaces’. D.A.H. was supported by the Charles Phelps Taft Research Center. A.L. was supported by NSF RTG Grant DMS-1045119. All three authors were supported by the NSF Grant DMS-1500454.
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Herron, D.A., Lukyanenko, A. & Tyson, J.T. Quasiconvexity in the Heisenberg group. Geom Dedicata 192, 157–170 (2018). https://doi.org/10.1007/s10711-017-0257-6
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DOI: https://doi.org/10.1007/s10711-017-0257-6