 Discriminant criterion for an alternating Galois group (source code)

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= Discriminant criterion for an alternating Galois group

For a monic separable polynomial over a field of characteristic other than two, its Galois group is contained in the alternating group exactly when its discriminant is a square in the base field. The Galois action multiplies the Vandermonde product by the sign of the induced root permutation.

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