The tame Hilbert symbol via K-theory and central extensions

Abstract

Let $K$ be a mixed characteristic local field whose residue field has cardinality $q$, and let $n$ be an integer dividing $q-1$. In the first part of this document we construct a $K$-theoretic enhancement of the $n$-th power residue symbol $K^\times \times K^\times \rightarrow \mu_n$. In the second part we construct central extensions of $GL_m(K)$ by $\mu_n$ and we express the $n$-th power residue symbol in terms of a symbol defined using the extension obtained for $m=1$. Our constructions both rely on the study of finite free pointed $\mu_n$-sets.