Fitting Ideals of Projective Limits of Modules over Non-Noetherian Iwasawa Algebras

Abstract

Greither and Kurihara proved a theorem about the commutativity of projective limits and Fitting ideals for modules over the classical equivariant Iwasawa algebra $\Lambda_G=\mathbb{Z}_p[[T]][G]$, where $G$ is a finite, abelian group and $\Bbb Z_p$ is the ring of $p$--adic integers, for some prime $p$. In this paper, we generalize their result first to the Noetherian Iwasawa algebra $\mathbb{Z}_p[[T_1, T_2, \cdots, T_n]][G]$ and, most importantly, to the non-Noetherian algebra $\mathbb{Z}_p[[T_1, T_2, \cdots, T_n, \cdots]][G]$ of countably many generators. The latter generalization is motivated by the recent work of Bley-Popescu on the geometric Equivariant Iwasawa Conjecture for function fields, where the Iwasawa algebra is not Noetherian, of the type described above. Applications of these results to the emerging field of non-Noetherian Iwasawa Theory will be given in an upcoming paper.