On the main conjecture of Iwasawa theory for certain non-cyclotomic $\mathbb{Z}_p$-extensions

TL;DR

This paper proves the main conjecture of Iwasawa theory for certain non-cyclotomic $Z_p$-extensions of imaginary quadratic fields, linking algebraic properties to special $L$-values and implications for elliptic curves and Leopoldt conjecture.

Contribution

It establishes the main conjecture of Iwasawa theory for a specific class of non-cyclotomic $Z_p$-extensions of imaginary quadratic fields, a case previously unresolved.

Findings

Proves the main conjecture for the Iwasawa module $X(H_ inf)$.

Shows that if $X(H_ inf)=0$, then relevant $L$-values are $p$-adic units.

Implications for BSD conjecture for certain CM elliptic curves and weak $p$-adic Leopoldt conjecture.

Abstract

Let $K=\mathbb{Q}(\sqrt{-q})$, where $q$ is any prime number congruent to $7$ modulo $8$, with ring of integers $\mathcal{O}$ and Hilbert class field $H$. Suppose $p\nmid [H:K]$ is a prime number which splits in $K$, say $p\mathcal{O}=\mathfrak{p}\mathfrak{p}^*$. Let $H_\infty=HK_\infty$ where $K_\infty$ is the unique $\mathbb{Z}_p$-extension of $K$ unramified outside $\mathfrak{p}$. Write $M(H_\infty)$ for the maximal abelian $p$-extension of $H_\infty$ unramified outside the primes above $\mathfrak{p}$, and set $X(H_\infty)=\mathrm{Gal}(M(H_\infty)/H_\infty)$. In this paper, we establish the main conjecture of Iwasawa theory for the Iwasawa module $X(H_\infty)$. As a consequence, we have that if $X(H_\infty)=0$, the relevant $L$-values are $\mathfrak{p}$-adic units. In addition, the main conjecture for $X(H_\infty)$ has implications toward (a) the BSD Conjecture for a class of CM elliptic curves; (b) weak $\mathfrak{p}$-adic Leopoldt conjecture.