Separability Keith Conrad
نویسنده
چکیده
From Definition 1.1, checking a polynomial is separable requires building a splitting field to check the roots are distinct. But we will see in Section 2 a criterion for deciding when a polynomial is separable (that is, has no multiple roots) without having to work in a splitting field. In Section 3 we will define what it means for a field extension to be separable and then prove the primitive element theorem, an important result about separable field extensions.
منابع مشابه
Separability Ii
Derivations are discussed in Appendix B. The proofs of Theorems 1.1 and 1.2 both use tensor products. For those two proofs, the reader should be comfortable with the fact that injectivity and surjectivity of a linear map of vector spaces can be detected after a base extension: a linear map is injective or surjective if and only if its base extension to a larger field is injective or surjective....
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For any field K, a field K(ζn) where ζn is a root of unity (of order n) is called a cyclotomic extension of K. The term cyclotomic means circle-dividing, and comes from the fact that the nth roots of unity divide a circle into arcs of equal length. We will see that the extensions K(ζn)/K have abelian Galois groups and we will look in particular at cyclotomic extensions of Q and finite fields. T...
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