Definition. conjugate constituents and the inertia subgroup [fgap-001O]

Let \(N\trianglelefteq G\), let \(V\) be a \(G\)-representation, and let \(W\subseteq V|_N\) be an irreducible \(N\)-subrepresentation. For \(g\in G\), the conjugate representation \(,{}^gW\) has the same vector space and action \[ n\cdot _g w=(g^{-1}ng)\cdot w. \] The inertia subgroup of \(W\) is \[ I_G(W)=\{g\in G:{}^gW\cong W\}. \] The isomorphism classes of conjugates form a \(G\)-orbit, with stabilizer \(I_G(W)\). See [lux2010representations, sec. 3.6, pp. 222--225].