arXiv subjects

Tom Ferragut

Publications and source records attributed to Tom Ferragut.

3 recordsLinked to original sources

arXiv2022

Geometric rigidity of quasi-isometries in horospherical products

We prove that quasi-isometries of horospherical products of hyperbolic spaces are geometrically rigid in the sense that they are uniformly close to product maps, this is a generalisation of the result obtained by Eskin, Fisher and Whyte in [7]. Our work covers the case of solvable Lie groups of the form R ___ (N 1 x N 2), where N 1 and N 2 are nilpotent Lie groups, and where the action on R contracts the metric on N 1 while extending it on N 2. We obtain new quasi-isometric invariants and classi cations for these spaces.

math.DG↗

arXiv2020

Geodesics and Visual boundary of Horospherical Products

We study the geometry of horospherical products by providing a description of their distances, geodesics and visual boundary. These products contains both discrete and continuous examples, including Cayley graphs of lamplighter groups and solvable Lie groups of the form IR semi-direct product with (N1 xN2), where N1 and N2 are two simply connected, nilpotent Lie groups.

math.MG↗

arXiv2018

Elementary solution of an infinite sequence of instances of the Hurwitz problem

We prove that there exists no branched cover from the torus to the sphere with degree 3h and 3 branching points in the target with local degrees (3,...,3), (3,...,3), (4,2,3,...,3) at their preimages. The result was already established by Izmestiev, Kusner, Rote, Springborn, and Sullivan, using geometric techniques, and by Corvaja and Zannier with a more algebraic approach, whereas our proof is topological and completely elementary: besides the definitions, it only uses the fact that on the torus a simple closed curve can only be trivial (in homology, or equivalently bounding a disc, or equivalently separating) or non-trivial.

math.GT↗