The **Weyl group** associated to a subgroup $H \subseteq G$ is the quotient $W = N_G(H) / Z_G(H)$ of the normalizer of $H$ by the centralizer of $H$. The terminology is taken from the theory of Lie groups, where there is a unique conjugacy class of maximal tori in a Lie group $G$ and if $T$ is any such maximal torus then $Z_G(T) = T$ has finite index in $N_G(T)$. In that context we may thus speak of the Weyl group of $G$.

When $G$ is an abstract group, we must specify $H$ as well, and the Weyl group naturally embeds into the automorphism group $\Aut(H)$ and gives the subset of automorphisms of $H$ that are induced by conjugation within $G$.

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- Last edited by John Jones on 2022-06-27 19:12:08

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