 Invariant bilinear form as an intertwiner (source code)

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= Invariant bilinear form as an intertwiner

A bilinear form $B$ on $V$ is invariant exactly when $v\mapsto B(v,-)$ is a $G$-homomorphism $V\to V^*$. On an irreducible representation, Schur's lemma makes a nonzero such form <nondegenerate bilinear form>[nondegenerate] and unique up to scale.

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