Homogeneous spaces, algebraic $K$-theory and cohomological dimension of fields

Abstract

Let $q$ be a non-negative integer. We prove that a perfect field $K$ has cohomological dimension at most $q + 1$ if, and only if, for any finite extension $L$ of $K$ and for any homogeneous space $Z$ under a smooth linear connected algebraic group over $L$, the $q$-th Milnor $K$-theory group of $L$ is spanned by the images of the norms coming from finite extensions of $L$ over which $Z$ has a rational point. We also prove a variant of this result for imperfect fields.