Abstract
In this paper, we give an equivariant compactification of the space \({\mathbb {P}}{\text {Flat}}(\Sigma )\) of homothety classes of half-translation structures on a compact, connected, orientable surface \(\Sigma \). We introduce the space \({\mathbb {P}}{\text {Mix}}(\Sigma )\) of homothety classes of mixed structures on \(\Sigma \), that are \({\text {CAT}}(0)\) tree-graded spaces in the sense of Drutu and Sapir, with pieces which are \({\mathbb {R}}\)-trees and completions of surfaces endowed with half-translation structures. Endowing \({\text {Mix}}(\Sigma )\) with the equivariant Gromov topology, and using asymptotic cone techniques, we prove that \({\mathbb {P}}{\text {Mix}}(\Sigma )\) is an equivariant compactification of \({\mathbb {P}}{\text {Flat}}(\Sigma )\), thus allowing us to understand in a geometric way the degenerations of half-translation structures on \(\Sigma \). We finally compare our compactification to the one of Duchin–Leininger–Rafi, based on geodesic currents on \(\Sigma \), by the mean of the translation distances of the elements of the covering group of \(\Sigma \).
Résumé
Dans cet article, on construit une compactification équivariante de l’espace \({\mathbb {P}}{\text {Flat}}(\Sigma )\) des classes d’homothétie de structures de demi-translation sur une surface \(\Sigma \) compacte, connexe, orientable. On définit l’espace \({\mathbb {P}}{\text {Mix}}(\Sigma )\) des classes d’homothétie de structures mixtes sur \(\Sigma \), qui sont des structures arborescentes, au sens de Drutu et Sapir, \({\text {CAT}}(0)\), dont les piéces sont des arbres réels ou des complétés de surfaces munies de structures de demi-translation. En munissant \({\text {Mix}}(\Sigma )\) de la topologie de Gromov équivariante, et en utilisant des techniques de cônes asymptotiques à la Gromov, on montre que \({\mathbb {P}}{\text {Mix}}(\Sigma )\) est une compactification équivariante de \({\mathbb {P}}{\text {Flat}}(\Sigma )\), ce qui nous permet de comprendre géométriquement les dégénérescences de structures de demi-translation sur \(\Sigma \). On compare ensuite cette compactification à celle de Duchin–Leininger–Rafi, qui utilise des courants géodésiques, en passant par les distances de translation des éléments du groupe de revêtement de \(\Sigma \).
Similar content being viewed by others
References
Benoist, Y., Hulin, D.: Cubic differentials and finite volume convex projective surfaces. Geom. Topol. 17, 595–620 (2013)
Bridson, M.R., Haefliger, A.: Metric spaces of non-positive curvature. Grund. Math. Wiss. 319, Springer, Berlin (1999)
Bonahon, F.: Geodesic laminations on surfaces. In: Laminations and Foliations in Dynamics, Geometry and Topology (stony Brook, 1998) Contemp. Math. Amer. Math. Soc. 269 (2001)
Bonahon, F.: The geometry of Teichmüller space via geodesic currents. Invent. Math. 92, 139–162 (1988)
Bourbaki, N.: Topologie générale. Chap. 1 à 4, Hermann, Paris (1971)
Choi, S., Goldman, W.: The classification of real projective structures on compact surfaces. Bull. Am. Math. Soc. 34, 161–171 (1997)
Dankwart, K.: On the large-scale geometry of flat surfaces. Dissertation zur Erlangung des Doktorgrades (Bonn, 010)
Duchin, M., Leininger, C., Rafi, K.: Length spectra and degeneration of flat metrics. Invent. Math. 18, 231–277 (2010)
Druţu, C.: Cônes asymptotiques et invariants de quasi-isométrie pour des espaces métriques hyperboliques. Ann. Inst. Fourier (Grenoble) 51, 81–97 (2001)
Druţu, C., Sapir, M.: Tree-graded spaces and asymptotic cones of groups. Topology 44, 959–1058 (2005)
Dugundji, J.: Topology. Wm. C. Brown, Dubuque (1989)
Fathi, A., Laudenbach, F., Poenaru, V.: Travaux de Thurston sur les surfaces. Astérisque, no. 66–67, 284 p. Société Mathématique de France, Paris (1979)
Goldman, W.M.: Geometric structures on manifolds and varieties of representations. In: Geometry of Group Representations (Boulder, 1987), pp. 169–198, Contemp. Math. 74, Amer. Math. Soc. (1988)
Gromov, M.: Asymptotic invariants of infinite groups. “Geometric group theory” Vol. 2, (Sussex, 1991). In: Niblo, A., Roller, M. (eds.) Theory, Geometric Group, 182nd edn. LMS LNS. Cambridge University Press, Cambridge (1993)
Labourie, F.: Flat projective structures on surfaces and cubic holomorphic differentials. Pure Appl. Math. 4(part 1), 1057–1099 (2007)
Levitt, G.: Foliations and laminations on hyperbolic surfaces. Topology 114, 119–135 (2004)
Loftin, J.: Flat metrics, cubic differentials and limits of projective holonomies. Geom. Dedic. 128, 97–106 (2007)
Minsky, Y.N.: Harmonic maps, length, and energy in Teichmüller space. J. Differ. Geom. 35, 151–217 (1992)
Morzadec, T.: Compactification géométrique de l’espace des modules des structures de demi-translation sur une surface, Thèse de doctorat. http://www.math.u-psud.fr/~morzadec/ultraplat.pdf
Morzadec, T.: Laminations géodésiques plates. À paraître dans Ann. Institut Fourier (Grenoble) arXiv:1311.7586
Morgan, J., Shalen, P.: Free actions of surface groups on \({\mathbb{R}}\)-trees. Topology 30, 143–154 (1991)
Otal, J.-P.: Le théorème d’hyperbolisation pour les variétés fibrées de dimension 3. Astérisque 235, Société Mathématique de France, Paris (1996)
Paulin, F.: Sur la compactification de Thurston de l’espace de Teichmüller. dans “Géométries à courbure négative ou nulle, groupes discrets et rigidités”, L. Bessières, A. Parreau, B. Remy eds (Actes de l’école d’été de l’Institut Fourier, Grenoble, 2004), Sémi. Congrès 18, 421–443, Soc. Math. France (2009)
Paulin, F.: The Gromov topology on \({\mathbb{R}}\)-trees. Topol. Appl. 32, 197–221 (1989)
Paulin, F.: Topologie de Gromov équivariante, structures hyperboliques et arbres réels. Invent. Math. 94, 53–80 (1988)
Rafi, K.: A characterization of short curves of a Teichmüller geodesic. Geom. Topol. 9, 179–202 (2005)
Shalen, P.: Dendrology of groups: an introduction. In: Gersten, S.M. (ed.) Essays in Group Theory. Mathematical Sciences Research Institute Publications, vol. 8, pp. 265–319. Springer, New York (1987)
Skora, R.: Splittings of surfaces. J. Am. Math. Soc. 9, 605–616 (1996)
Strebel, K.: Quadratic Differentials. Springer, New York (1984)
Wright, A.: Translation surfaces and their orbit closures: an introduction for a broad audience. Geom. Topol. 15, 1225–1295 (2011)
Zorich, A.: Flat surfaces. In: Cartier, P., Julia, B., Moussa, P., Vanhove, P. (eds.) Frontiers in Number Theory, Physics and Geometry. Vol. 1: On Random Matrices, Zeta Functions and Dynamical Systems, pp. 439–586. Springer, NewYork (2006)
Acknowledgements
I want to thank Frédéric Paulin for many advices and corrections that have deeply improved the writting of this paper. Funding was provided by École Polytechnique, Université Paris-Saclay, Université Paris-Sud.
Author information
Authors and Affiliations
Corresponding author
About this article
Cite this article
Morzadec, T. Geometric compactification of moduli spaces of half-translation structures on surfaces. Geom Dedicata 193, 31–72 (2018). https://doi.org/10.1007/s10711-017-0256-7
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10711-017-0256-7
Keywords
- Half-translation surface
- Holomorphic quadratic differential
- Tree-graded space
- Mixed structure on surfaces
- Asymptotic cone
- Flat surface with singularities
- Geodesic lamination
- Compactification