arXiv subjects
Publications and source records attributed to Manabu Ozaki.
Let $G$ be a finite $p$-group. We construct a $G$-extension $K/k$ of number fields such that the $p$-adic completion of the unit group of $K$ has a prescribed $\mathbb{Z}_p[G]$-module structure, up to free direct summands.
In the present paper, we provide a new analogy between number fields and 1-dimensional function fields over finite fields from the viewpoint that the maximal cyclotomic extension of a number field is analogous to the constant field extension of a function field to an algebraic closure. Namely, we give a number field analogue of the Grothendieck conjecture for hyperbolic curves over finite fields proved by Tamagawa and Mochizuki, which is an affirmative answer to Conjecture(12.5.3) of ``Cohomology of number fields" by Neukirch-Schmidt-Wingberg in the case where the ramified prime sets are empty.
For any finite cyclic $p$-group $G$, we will show that every $\mathbb{Z}_p$-torsion free finitely generated $\mathbb{Z}_p[G]$-module appears as $\mathcal{O}_K^\times\otimes_{\mathbb{Z}}\mathbb{Z}_p$ up to $\mathbb{Z}_p[G]$-free direct summands for a certain $G$-extension $K/k$ of number fields.
Let $K/k$ be a pro-$p$-extension over a number field $k$ whose Galois group is finitely generated and $k_0\subseteq k_1\subseteq\cdots\subseteq k_n\subseteq\cdots$ an ascending sequence of intermediate fields of $K/k$ such that $k_n/k$ is normal, $[k_n:k]<\infty$ and $\bigcup_{n\ge 0} k_n=K$. We will show by using representation theory of finite groups that the non-$p$-part $h_n(p')$ of the class number of $k_n$ converges $p$-adically as $n\rightarrow\infty$, and the limit is independent to the choice of $k_n$'s. Also, in the case where $K/k$ is the cyclotomic $\mathbb{Z}_p$-extension over an abelian number field $k$, we will take an analytic approach and obtain certain enigmatic relationships between the $p$-adic limits of vaious arithmetic invariants along $K/k$, namely, the class number, the ratio of $p$-adic regulator and the square root of the discriminant, and the order of the algebraic $K_2$-group of the ring of integers.
Let $K$ be a function field of one variable over a finite field $\mathbb{F}$. Weil's celebrated theorem states that the congruent zeta function of $K/\mathbb{F}$ is determined by the $\mathrm{Gal}(\overline{\mathbb{F}}/\mathbb{F})$-module structure of $X_{\overline{\mathbb{F}}K}(p)\otimes_{\mathbb{Z}_p}\mathbb{Q}_p$, and vise versa, where $p$ is a prime number different from the characteristic of $K$ and $X_{\overline{\mathbb{F}}K}(p)$ stands for the Galois group of the maximal unramified abelian $p$-extension over $\overline{\mathbb{F}}K$. In the present paper, I will give a number field analogue of the above mentioned theorem by considering the total cyclotomic extension, which we may regard as a number field analogue of $\overline{\mathbb{F}}K/K$.
For a prime number p, we denote by K the cyclotomic Z_p-extension of a number field k. For a finite set S of prime numbers, we consider the S-ramified Iwasawa module which is the Galois group of the maximal abelian pro-p-extension of K unramified outside S. This paper treats the case where S does not contain p and k is the rational number field or an imaginary quadratic field. In this case, we prove the explicit formulae for the free ranks of the S-ramified Iwasawa modules as abelian pro-p groups, by using Brumer's p-adic version of Baker's theorem on the linear independence of logarithms of algebraic numbers.
For any finite group G and integer i, let $\mathcal{H}^i(G)$ be the set of all the isomorphism classes of the Galois cohomology groups $\hat{H}^i(K/k,E_K)$, where K/k runs over all the unramified G-extension of number fields and E_K denotes the global unit group of K. We will determine $\mathcal{H}^i(G)$ for i=0,1,2, and 4 in the case where G is a finite p-group.
We will show that if $K$ is a knot of prime period $p>2$ and whose Alexander polynomial $Δ_K(t)$ is monic and of degree $p-1$, then $Δ_K(t)$ is uniquely determined only by $p$.
In the present paper, we shall show that for any prime number p, every finite p-group occurs as the Galois Group of the maximal unramified p-extension over a certain number field of finite degree. We shall also show that for any given pro-p-group G with countably many generators, there exists a number field (not necessary of finite degree) whose maximal unramified p-extension has Galois group isomorphic to G. This means that the set of the isomorphism classes of the Galois groups of the maximal unramified p-extensions over the number fields (including of infinite degree) is precisely equal to that of all the pro-p-groups with countably many generators.
Let S be a set of n ideals of a commutative ring A. Let G_{even} (respectively G_{odd}) denote the product of all the sums of even (respectively odd) number of ideals of S. If n<7 the product of G_{even} and the intersection of all ideals of S is included in G_{odd}. In the case A is an Noetherian integral domain, this inclusion is replaced by equality if and only if A is a Dedekind domain.