Abstract:
Let ℓ be a regular odd prime, k the ℓ th cyclotomic field and K=k(ℓ√a), where a is a positive integer. Under the assumption that there are exactly three places not over ℓ
that ramify in K∞/k∞, we continue to study the structure of the Tate module (Iwasawa module) Tℓ(K∞) as a Galois module. In the case ℓ=3, we prove that for finite Tℓ(K∞) we have |Tℓ(K∞)|=ℓr
for some odd positive integer r. Under the same assumptions, if ¯Tℓ(K∞) is the Galois group of the maximal unramified Abelian ℓ-extension of K∞, then the kernel of the natural epimorphism ¯Tℓ(K∞)→Tℓ(K∞) is of order 9. Some other results are obtained.
Keywords:
Iwasawa theory, Tate module, extensions with restricted ramification.