Recent papers

Optimal higher-dimensional Dehn functions for some CAT(0) lattices; Groups Geom. Dyn. 8 (2014), no. 2, 441–466.
Reduction theory for mapping class groups and applications to moduli spaces, J. Reine Angew. Math. 649, (2010), 11-31.
(with L. Ji), The asymptotic Schottky problem, GAFA 19, (2010), 1693-1712.
(with S. Geninska), A geometric characterization of arithmetic Fuchsian groups, Duke Math. J., 142, (2008), 111-125.
On the characterization of arithmetic groups among arbitrary discrete subgroups of Lie groups, in: Ji, L. (ed.). Selected papers of the conference on geometry, topology and analysis of locally symmetric spaces and discrete groups, Beijing, China, July 17--August 4, 2006. Advanced Lectures in Math. (ALM), 6, 259-270 (2008).
Entropy of the geodesic flow for metric spaces and Bruhat-Tits buildings, Adv. Geom., 6, (2006), 475-491.
On polyhedral retracts and compactifications of locally symmetric spaces, Diff. Geom. Appl.,20, (2004), 293-318.
(with Ch. Pittet), On quadratic Dehn functions, Math. Z., 248, (2004), 725-755.
Tits geometry, arithmetic groups, and the proof of a conjecture of Siegel, J. Lie Theory, 14, (2004), 317-338.
Isoperimetric inequalities and random walks on quotients of graphs and buildings, Math. Z., 248, (2004), 101-112.
Bi-Lipschitz embeddings of trees into Euclidean buildings,Geom. Dedicata, 102, (2003), 109-125.
Critical exponents of discrete groups and L² -spectrum, Proc. AMS 132 (2003), 919-927.
Kazhdan's property (T), L²-spectrum and isoperimetric inequalities for locally symmetric spaces, Comment. Math. Helv. 78 (2003), 116-133.