Coarse cohomology types of pure meta cyclic fields

Abstract

An unexpected behavior of pure septic fields L = Q(D^1/7) with certain prime radicands D congruent to 2 or 4 modulo 7, which split in the cyclotomic field of seventh roots of unity, is proved by direct computation. Whereas the Galois closures N = Q(zeta_7, D^1/7) of these fields contain relative differential principal factorizations in the kernel of the norm of N/L, the class numbers of L and N are not divisible by 7.