Transfer ideal of conjugation-fixed elements
= Transfer ideal of conjugation-fixed elements
{title2=$A_H^G$}
Let a finite group $G$ act on an algebra $A$ by conjugation and let $H\leq G$. The transfer ideal from $H$ is
$$
A_H^G=\operatorname{Tr}_H^G(A^H)\subseteq A^G,
\qquad
\operatorname{Tr}_H^G(a)=\sum_{g\in G/H}gag^{-1}.
$$
The notation records both the source subgroup and the ambient fixed-point algebra.