A characterization of Gromov hyperbolicity of surfaces with variable negative curvature.
A. D. Alexandrov's problem for -spaces.
A differential geometric characterization of symmetric spaces of higher rank
A new characterization of Gromov hyperbolicity for negatively curved surfaces.
In this paper we show that to check Gromov hyperbolicity of any surface of constant negative curvature, or Riemann surface, we only need to verify the Rips condition on a very small class of triangles, namely, those obtained by marking three points in a simple closed geodesic. This result is, in fact, a new characterization of Gromov hyperbolicity for Riemann surfaces.
A new obstruction to embedding Lagrangian tori.
A Non-Probabilistic Proof of the Assouad Embedding Theorem with Bounds on the Dimension
We give a non-probabilistic proof of a theorem of Naor and Neiman that asserts that if (E, d) is a doubling metric space, there is an integer N > 0, depending only on the metric doubling constant, such that for each exponent α ∈ (1/2; 1), one can find a bilipschitz mapping F = (E; dα ) ⃗ ℝ RN.
A rough curvature-dimension condition for metric measure spaces
We introduce and study a rough (approximate) curvature-dimension condition for metric measure spaces, applicable especially in the framework of discrete spaces and graphs. This condition extends the one introduced by Karl-Theodor Sturm, in his 2006 article On the geometry of metric measure spaces II, to a larger class of (possibly non-geodesic) metric measure spaces. The rough curvature-dimension condition is stable under an appropriate notion of convergence, and stable under discretizations as...
Actions of discrete groups on nonpositively curved spaces.
An Overview of the Proof of the Splitting Theorem in Spaces with Non-Negative Ricci Curvature
Applications of the ‘Ham Sandwich Theorem’ to Eigenvalues of the Laplacian
We apply Gromov’s ham sandwich method to get: (1) domain monotonicity (up to a multiplicative constant factor); (2) reverse domain monotonicity (up to a multiplicative constant factor); and (3) universal inequalities for Neumann eigenvalues of the Laplacian on bounded convex domains in Euclidean space.
Asymptotic dimension of coarse spaces.
Asymptotic geometry of arithmetic quotients of symmetric spaces.
Asymptotic isoperimetry of balls in metric measure spaces.
In this paper, we study the asymptotic behavior of the volume of spheres in metric measure spaces. We first introduce a general setting adapted to the study of asymptotic isoperimetry in a general class of a metric measure space...
Atoroïdalité complète et annulation de l’invariant de Perelman
On résume les proprietés de l’invariant de Perelman, et en combinaison avec l’invariant de Yamabe on exprime certaines proprietés géométriques des variétés de dimension en fonction de . On décrit des exemples d’annulation de en dimension , où on trouve des liens entre l’effondrement et l’existence de métriques à courbure scalaire positive. On montre qu’une version d’atoroïdalité qu’on appelle atoroïdalité complète est détectée par sur les variétés de courbure négative ou nulle de dimension...
Au bord de certains polyèdres hyperboliques
Le cadre de cet article est celui des groupes et des espaces hyperboliques de M. Gromov. Il est motivé par la question suivante : comment différencier deux groupes hyperboliques à quasi-isométrie près ? On illustre ce problème en détaillant un exemple de M. Gromov issu de Asymptotic invariants for infinite groups. On décrit une famille infinie de groupes hyperboliques, deux à deux non quasi-isométriques, de bord la courbe de Menger. La méthode consiste à étudier leur structure quasi-conforme au...
Bas du spectre et delta-hyperbolicité en géométrie de Hilbert plane
On montre l’équivalence entre l’hyperbolicité au sens de Gromov de la géométrie de Hilbert d’un domaine convexe du plan et la non nullité du bas du spectre de ce domaine.
Coarse topology, enlargeability, and essentialness
Using methods from coarse topology we show that fundamental classes of closed enlargeable manifolds map non-trivially both to the rational homology of their fundamental groups and to the -theory of the corresponding reduced -algebras. Our proofs do not depend on the Baum–Connes conjecture and provide independent confirmation for specific predictions derived from this conjecture.
Cohomologie quantique
Collapsed Riemannian Manifolds with Bounded Diameter and Bounded Covering Geometry.
Collapsing and soul theorem in three-dimension