2 citations · 2 across the 5 of their papers we have counts for
5 papers
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…
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…
Mapping class groups and outer automorphism groups of free groups are C*-simple
Martin R. Bridson, Pierre de la Harpe
We prove that the reduced C*-algebras of centerless mapping class groups and outer automorphism groups of free groups are simple, as are the irreducible pure subgroups of mapping c…