B2.9

Number Fields
Part II, 2003

By Dedekind's theorem, or otherwise, factorise 2,3,52,3,5 and 7 into prime ideals in the field K=Q(34)K=\mathbb{Q}(\sqrt{-34}). Show that the ideal equations

[ω]=[5,ω][7,ω],[ω+3]=[2,ω+3][5,ω+3]2[\omega]=[5, \omega][7, \omega], \quad[\omega+3]=[2, \omega+3][5, \omega+3]^{2}

hold in KK, where ω=1+34\omega=1+\sqrt{-34}. Hence, prove that the ideal class group of KK is cyclic of order 4.4 .

[It may be assumed that the Minkowski constant for KK is 2/π2 / \pi.]