Preprints:

CAT(0) 4-manifolds are Euclidean (with Koichi Nagano and Stephan Stadler)

Curvature bounds of subsets in dimension two (with Stephan Stadler)

Cyclic projections in Hadamard spaces (with Anton Petrunin)

Lorentz meets Lipschitz (with Christian Lange und Clemens Sämann)

Weak topology on CAT(0) spaces (with Anton Petrunin)

Struktur der Submetrien (Part of the Ph.D. thesis)

Papers Published or Accepted for Publication

• Publikationsliste (2021)

About every convex set in any generic Riemannian manifold J. Reine Angew. Math., to appear (with Anton Petrunin)

A diameter gap for quotients of the unit sphere J. Eur. Math. Soc., to appear, (with Claudio Gorodski, Christian Lange, Ricardo Mendes)

Topological regularity of spaces with an upper curvature bound J. Eur. Math. Soc., to appear, (with Koichi Nagano)

Ricci curvature in dimension two J. Eur. Math. Soc., to appear, (with Stephan Stadler)

Structure of submetries Geom. Topol., to appear, (with Vitali Kapovitch)

Remarks on manifolds with two-sided curvature bounds Anal. Geom. Metr. Spaces 9 (2021), 53-64 to (with Vitali Kapovitch)

Short retractions of CAT(1) spaces Proc. Amer. Math. Soc. 149 (2021), 1247-1257 (with Anton Petrunin)

Metric measure boundary and geodesic flow on Alexandrov spaces J. Eur. Math. Soc. 23 (2021), 29-62 (with Vitali Kapovitch, Anton Petrunin )

Improvements of upper curvature bounds Trans. Amer. Math. Soc. 373 (2020), 7153-7166 (with Stephan Stadler)

Canonical parametrization of metric discs Duke Math. J. 169 (2020), 761-797 (with Stefan Wenger)

Dehn functions and Hölder extensions in asymptotic cones J. Reine Angew. Math. 763 (2020), 79-109 (with Stefan Wenger, Robert Young)

Rigidity of Busemann convex Finsler metrics Comment. Math. Helv. 94 (2019), 855-868 (with Sergei Ivanov)

Conformal deformation of CAT(0) spaces Math. Ann. 373 (2019), 155-163 (with Stephan Stadler)

Geodesically complete spaces with an upper curvtaure bound Geom. Funct. Anal. 29 (2019), 159-202 (with Koichi Nagano )

Intrinisic structure of minimal discs in metric spaces Geom. Topol. 22 (2018), 591-644 (with Stefan Wenger)

Isoperimetric characterization of upper curvtaure bounds Acta Math. 221 (2018), 159-202 (with Stefan Wenger )

Algebraic nature of singular Riemannian foliations in spheres J. Reine Angew. Math. 744 (2018), 265-273 (with Marco Radeschi )

Area minimizing discs in metric spaces Arch. Rational Mech. Anal. 223 (2017), 1123-1182 (with Stefan Wenger)

Energy and area minimizers in metric spaces Adv. Calc. Var. 10 (2017), 407-421 (with Stefan Wenger )

The curvature of orbit spaces Geom. Dedicata 190 (2017), 135-142 (with Claudio Gorodski )

Riemannian foliations of spheres Geom. Topol. 20 (2016), 1257-1274 (with Burkhard Wilking)

Isometric actions on spheres with an orbifold quotient Math. Ann. 365 (2016), 1041-1067 (with Claudio Gorodski)

Regularity of harmonic discs in spaces with quadratic isoperimetric inequality Calc. Var. Partial Differential 55 (2016), 55-98 (with Stefan Wenger)

Riemannian foliations on contractible manifolds Münster J. Math. 8 (2015), 1-16 (with Luis Florit, Oliver Goertsches, Dirk Töben)

Polar foliations on symmetric spaces Geom Funct. Anal. 24 (2014), 1298-1315

Homogeneous compact geometries Transform. Groups 19 (2014), 793-852 (with Linus Kramer)

On orbit spaces of representations of compact Lie groups J. Reine Angew. Math. 691 (2014), 61-100 (with Claudio Gorodski)

Polar actions on symmetric spaces of higher rank Bull. London Math. Soc. 45 (2013), 341-350 (with Andreas Kollross)

On contractible orbifolds Proc. Amer. Math. Soc. 141 (2013), 3303-3304

Affine images of Riemannian manifolds Math. Z. 270 (2012), 809-817

On smoothness of isometries between orbit spaces Riemannian geometry and Applications -Proceedings RIGA (2011), 17-28 (with Marcos Alexandrino)

Curvature explosion in quotients and applications J. Differential Geom. 85 (2010), 117-140 (with Gudlaugur Thorbergsson)

Geometric resolution of singular Riemannian foliations Geom. Dedicata 149 (2010), 379-395

At infinity of finite-dimensional CAT(0) spaces Math. Ann. 346 (2010), 1-21 (with Pierre-Emmanuel Caprace)

Notes on the Jacobi equation Differential Geom. Appl. 27 (2009), 329-334

Singular Riemannian foliations on spaces without conjugate points Proceedings of VIII International Colloquium on Differential Geometry (2009), 75-82

The de Rham decomposition theorem for metric spaces Geom. Funct. Anal. 18 (2008), 120-143 (with Thomas Foertsch)

Non-positive curvature and the Ptolemy inequality Int. Math. Res. Not. 22 (2007), Art. ID rnm100 (with Thomas Foertsch and Viktor Schroeder)

Affine functions on CAT(k) spaces Math. Z. 255 (2007), 231-244 (with Viktor Schroeder)

Spaces with many affine functions Proc. Amer. Math. Soc. 135 (2007), 2263-2271 (with P. Hitzelberger)

Variationally complete actions on nonnegatively curved manifolds Illinois J. Math. 51 (2007), 605-615 (with G. Thorbergsson)

Tangent spaces and Gromov-Hausdorff limits of subanalytic spaces J. Reine Angew. Math. 608 (2007), 1-15 (with Andreas Bernig)

On Hoelder continuous Riemannian and Finsler metrics Trans. Amer. Math. Soc. 358 (2006), 2917-2926 (with Asli Yaman)

Building-like spaces J. Math. Kyoto Univ. 46 (2006), 789-805 (with Andreas Balser)

Rigidity of spherical buildings and joins Geom. Funct. Anal. 15 (2005), 720-752

Almost convex subsets Geom. Dedicata 115 (2005), 201-218

Centers of convex subsets of buildings Ann. Global Anal. Geom. 28 (2005), 201-209 (with Andreas Balser)

Open map theorem in metric spaces Algebra i Analiz 17 (2005), 139-159

On the geometry of subsets of positive reach Manuscripta Math. 115 (2004), 199-205

Differentiation in metric spaces Algebra i Analiz 16 (2004), 128-161

Metric characterizations of spherical and Euclidean buildings Geom. Topol. 5 (2001), 521-550 (with Ruth Charney)