Definition 63.15.2. Let $f : P\to P$ be an endomorphism of a finite projective $\Lambda [G]$-module $P$. We define

$\text{Tr}_{\Lambda }^ G(f; P) := \varepsilon \left(\text{Tr}_{\Lambda [G]}(f; P)\right)$

to be the $G$-trace of $f$ on $P$.

In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar).