Paper 4, Section II, H

Galois Theory
Part II, 2014

(i) Let GG be a finite subgroup of the multiplicative group of a field. Show that GG is cyclic.

(ii) Let Φn(X)\Phi_{n}(X) be the nnth cyclotomic polynomial. Let pp be a prime not dividing nn, and let LL be a splitting field for Φn\Phi_{n} over Fp\mathbb{F}_{p}. Show that LL has pmp^{m} elements, where mm is the least positive integer such that pm1(modn)p^{m} \equiv 1(\bmod n).

(iii) Find the degrees of the irreducible factors of X351X^{35}-1 over F2\mathbb{F}_{2}, and the number of factors of each degree.