MA 542 A1 — Fall 2019
Abstract Algebra
REVIEW SHEET FOR NEW MATERIAL FOR FINAL
Definitions
- algebraic/transcendental elements over a field
- minimum polynomial (equivalently irreducible polynomial)
- degree of an algebraic element over a field
- linear independence of vectors in a vector space
- basis of a vector space
- algebraic extension of fields
- finite extension of fields
- degree of a finite extension of fields
- an algebraically closed field
- an automophism of a field
- an automorphism of a field K fixing a subfield F
- an algebraic closure of a field
- a splitting field of a family of polynomials
- multiplicity of a zero of a polynomial
- an embedding of fields
- an embedding of fields over F
- a normal extension
- a separable extension
- a Galois extension
Theorems from class that you should know how to prove:
- the minimum polynomial is irreducible
- F(alpha) is isomorphic to F[x]/(irr(alpha,F))
- finite extensions are algebraic
- K/Q a field extension and phi an automorphism of K implies that phi fixes Q.
- K/F algebraic and phi an automorphism of K which fixes F. Then phi(alpha) is a zero of irr(alpha,F).
- F is a characteristic 0 field, alpha is a zero of g(x) with multiplicity e, then alpha is a zero of g'(x) with
multiplicity e-1.
- If K is a splitting field over F, then every embedding tau of K into F over F
satisfies tau(K) is contained in K.
- If L/K/F are a tower of fields and L/F is separable, then L/K and K/F are separable.
- If E is a subfield of a Galois extension K/F, then K^Gal(K/E) = E.