Weak approximation and non-abelian fundamental groups
Weak approximation and non-abelian fundamental groups
We introduce a new obstruction to weak approximation which is related to étale non-abelian coverings of a proper and smooth algebraic variety X defined over a number field k. This enables us to give some counterexamples to weak approximation which are not accounted for by the Brauer–Manin obstruction, for example …