Paper 1, Section II, I

Galois Theory
Part II, 2013

(i) Give an example of a field FF, contained in C\mathbb{C}, such that X4+1X^{4}+1 is a product of two irreducible quadratic polynomials in F[X]F[X]. Justify your answer.

(ii) Let FF be any extension of degree 3 over Q\mathbb{Q}. Prove that the polynomial X4+1X^{4}+1 is irreducible over FF.

(iii) Give an example of a prime number pp such that X4+1X^{4}+1 is a product of two irreducible quadratic polynomials in Fp[X]\mathbb{F}_{p}[X]. Justify your answer.

[Standard facts on fields, extensions, and finite fields may be quoted without proof, as long as they are stated clearly.]