29 citations · 38 across the 9 of their papers we have counts for
6 papers · 1 filter
The true prosoluble completion of a group: examples and open problems
Goulnara Arzhantseva, Pierre de la Harpe, Delaram Kahrobaei
The true prosoluble completion $P\Cal S (Γ)$ of a group is the inverse limit of the projective system of soluble quotients of . Our purpose is to describe examples and to po…
On simplicity of reduced C*-algebras of groups
Pierre de la Harpe
A countable group is C*-simple if its reduced C*-algebra is a simple algebra. Since Powers recognised in 1975 that non-abelian free groups are C*-simple, large classes of groups wh…
Decompositions de groupes par produit direct et groupes de Coxeter
Yves de Cornulier, Pierre de la Harpe
We provide examples of groups which are indecomposable by direct product, and more generally which are uniquely decomposable in direct products of indecomposable groups. Examples i…
Construction of spherical cubature formulas using lattices
Pierre De La Harpe, Claude Pache, Boris B. Venkov
We construct cubature formulas on spheres supported by homothetic images of shells in some Euclidian lattices. Our analysis of these cubature formulas uses results from the theory…
Expanding graphs, Ramanujan graphs, and 1-factor perturbations
Pierre de la Harpe, Antoine Musitelli
We construct (k+-1)-regular graphs which provide sequences of expanders by adding or substracting appropriate 1-factors from given sequences of k-regular graphs. We compute numeric…
Cubature formulas, geometrical designs, reproducing kernels, and Markov operators
Pierre De La Harpe, Claude Pache
Cubature formulas and geometrical designs are described in terms of reproducing kernels for Hilbert spaces of functions on the one hand, and Markov operators associated to orthogon…