Indecomposability of Ideals in Group Rings
Indecomposability of Ideals in Group Rings
Let $H$ be a subgroup of $G$ and let $I$ be the (two-sided) ideal of ${\mathbf {Z}}G$ generated by $\omega ({\mathbf {Z}}H)$. In this note, we show that $I$ is indecomposable as an ideal in ${\mathbf {Z}}G$. This extends a result of Linnell [1] and simplifies his argument somewhat.