Cyclicity and indecomposability in the Brauer group of a $p$-adic curve

Abstract

For a $p$-adic curve $X$, we study conditions under which all classes in the $n$-torsion of $Br(X)$ are $\mathbb{Z}/n$-cyclic. We show that in general not all classes are $\mathbb{Z}/n$-cyclic classes. On the other hand, if $X$ has good reduction and $n$ is prime to $p$, of if $X$ is an elliptic curve over ${\mathbb{Q}}_p$ with split multiplicative reduction and $n$ is a power of $p$, then we prove that all order $n$ elements of $Br(X)$ are $\mathbb{Z}/n$-cyclic. Finally, if $X$ has good reduction and its function field $K(X)$ contains all $p^2$-th roots of $1$, we show the existence of indecomposable division algebras over $K(X)$ with period $p^2$ and index $p^3$.

Greatly expanded from previous version, includes new results in sections 5 and 7

References in corpus (2)

• Applications of patching to quadratic forms and central simple algebras
• Period-index and u-invariant questions for function fields over complete discretely valued fields