11-1. Let E/F be a Galois extension with (E : F] > 1. (i) Must there...
4. Let G be the Galois group of a finite field extension E of F. Let H and H, be subgroups of G, and let Ki and K2 be intermediate fields between F and E. For any o EG, prove that K2 = OK if and only if H2 = oHo-1,
G. Shorter Questions Relating to Automorphisms and Galois Groups Let F be a field, and K a finite extension of F. Suppose a, b E K. Prove parts 1-3: 1 If an automorphism h of K fixes Fand a, then h fixes F(a). 3 Aside from the identity function, there are no a-fixing automorphisms of a(). [HINT: Note that aV2 contains only real numbers.] 4 Explain why the conclusion of part 3 does not contradict Theorem 1. G. Shorter Questions...
2. (10) Let p be an odd prime. Let f(x) E Q(x) be an irreducible polynomial of degree p whose Galois group is the dihedral group D2p of a regular p-gon. Prove that f(x) has either all real roots precisely one real root or 2. (10) Let p be an odd prime. Let f(x) E Q(x) be an irreducible polynomial of degree p whose Galois group is the dihedral group D2p of a regular p-gon. Prove that f(x) has either...
Complete the sketch of proof for Lemma 3.17: use theorems 3.16 and 2.5 f F is a finite dimensional separable extension of an infinite jheld Lemma 3.17. iEaa LenF. K(u) for some u ε . thern SKETCH OF PROOF. By Theorem 3.16 there is a finite dimensional Galois n field Fi of K that contains F. The Fundamental Theorem 2.5 implies that F, is finite and that the extension of K by F, has only finitely many intermediate AutA felds....
Let E = F(a) be a (simple) extension of F. wherea E E is algebraic over F. Suppose the degree of α over F is n Then every β E E can be expressed uniquely in the form β-bo-b10 + +b-1a-1 for some bi F. (a) Show every element can be written as f (a) for some polynomial f(x) E F (b) Let m(x) be the minimal polynomial of α over F. Write m(x) r" +an-11n-1+--+ n_1α α0. Use this...
9. Let E be an extension field of a field F. (1) What does it mean for an element z EE being algebraic over F? (2) What does it mean for an element z E E being transcendental over F? (3) Can you find any element r e C such that r is transcendental over Q? (4) Can you prove that if a E E is algebraic over F then (F(a): F] is finite? (5) Can you prove that if...
Exercise 1 Let E, FCC and let E 2F be a field. (a) Without using the primitive element theorem, show that [E : FI < oo if and only if (Hint: Tower law → [F(01, , , , a.) : F1 < oo. For the other direction, use induction on IE、F) (b) Suppose that E F(a Show that E is normal if and only if for every E Flai, . . . , α.) for some on. . . ....
8. Let n be a positive integer. The n-th cyclotomic polynomial Ф,a(z) E Z[2] is defined recursively in the following way: 1. Ф1(x)-x-1. 2. If n > 1, then Фп(x)- , (where in the product in the denomina- tor, d runs through all divisors of n less than n). . A. Calculate Ф2(x), Ф4(x) and Ф8(z): . B. n(x) is the minimal polynomial for the primitive n-th root of unity over Q. Let f(x) = "8-1 E Q[a] and ω...
Thee part question. Please answer all parts! Let E be a field of characteristic p > 0 (we proved p must always be prime). Verify that the ring homomorphism X : Z → E determined by sending χ : 1-1 E (the unity in E) ( so x(n)-n 1E wheren1E 1E 1E (n-times), x(-n)- nle for any n 1,2,3,... and X(0) 0E by definition of χ) is in fact a ring homomorphism with ker(X) = pZ. Úse the fundamental homomorphism...