Let $K$ be a finite degree $n$ separable extension of a field $F$, and $K^{gal}$ be its
Galois (or normal) closure.
The **Galois group** for $K/F$ is the automorphism group $\Aut(K^{gal}/F)$.

This automorphism group acts on the $n$ embeddings $K\hookrightarrow K^{gal}$ via composition. As a result, we get an injection $\Aut(K^{gal}/F)\hookrightarrow S_n$, which is well-defined up to the labelling of the $n$ embeddings, which corresponds to being well-defined up to conjugation in $S_n$.

We use the notation $\Gal(K/F)$ for $\Aut(K/F)$ when $K=K^{gal}$.

There is a naming convention for Galois groups up to degree $47$.

To specify a Galois group, you can give its GAP id (e.g. [8,3] or [16,7]), a name (e.g. C5 or S12) or a transitive group label (e.g. 7T2 or 11T5).

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- Review status: beta
- Last edited by David Roe on 2021-02-12 16:08:16

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