Cyclic algebra
= Cyclic algebra
{title2=$(E/K,\sigma,a)$}
For a cyclic extension $E/K$ of degree $m$ with generator $\sigma$ and $a\in K^{\times}$, the <cyclic algebra> is generated by $E$ and $u$ with $ub=\sigma(b)u$, $u^m=a$. It is a <central simple algebra> of degree $m$. Its Brauer class can also be written $(\chi,a)$, where $\chi(\sigma)=1/m$.