The defect of weak approximation for a reductive group over a global field
arXiv:2406.08017
Abstract
We compute the defect of weak approximation for a reductive group G over a global field K in terms of the algebraic fundamental group of G.
v7: 27 pages, including the listing of a Magma program; v8: 29 pages, including an appendix by J.-L. Colliot-Thélène