The Apollonian metric: limits of the comparison and bilipschitz properties.
We construct and study the unique random tiling of the hyperbolic plane into ideal hyperbolic triangles (with the three corners located on the boundary) that is invariant (in law) with respect to Möbius transformations, and possesses a natural spatial Markov property that can be roughly described as the conditional independence of the two parts of the triangulation on the two sides of the edge of one of its triangles.
In [Comput. Math. Appl. 41 (2001), 135--147], A. A. Ungar employs the Möbius gyrovector spaces for the introduction of the hyperbolic trigonometry. This Ungar's work plays a major role in translating some theorems from Euclidean geometry to corresponding theorems in hyperbolic geometry. In this paper we explore the theorems of Stewart and Steiner in the Poincaré disc model of hyperbolic geometry.
Nous développons une théorie de Voronoï géométrique. En l’appliquant aux familles classiques de réseaux euclidiens (par exemple symplectiques ou orthogonaux), nous obtenons notamment de nouveaux résultats de finitude concernant les configurations de vecteurs minimaux et les réseaux particuliers (par exemple parfaits) de ces familles. Les méthodes géométriques introduites sont également illustrées par l’étude d’objets voisins (formes de Humbert) ou analogues (surfaces de Riemann).