Questions tagged [iwasawa-theory]

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1 vote
2 answers
122 views

A question about generalized harmonic numbers modulo $p$

Let $p \equiv 1 \pmod{3}$ be a prime and denote $H_{n,m} = \sum_{k = 1}^n 1/k^m$ as the $n,m$-th generalized harmonic number. I'm interested in computing $H_{(p-1)/3,\, 2}$ and $H_{(p-1)/6,\,2}$ ...
1 vote
0 answers
116 views

$\mathbb{Z}_\ell$-extensions of global function fields

Given a number field $F$ and a prime $p$, it is natural to study Iwasawa theory over the cyclotomic $\mathbb{Z}_p$-extension of $F$, i.e., the unique $\mathbb{Z}_p$-extension of $F$ which is contained ...
2 votes
0 answers
137 views

Extending the analogy between cyclotomic units and elliptic units

There is a nice analogy between cyclotomic units and elliptic units given as follows: Cyclotomic units are related to special values of the Riemann Zeta function. This is because the logarithmic ...
3 votes
0 answers
94 views

question about Sinnott's proof of the Ferrero-Washington Theorem

I'm currently reading the paper "On the $\mu$-invariant of the Γ-transform of a rational function" by W Sinnott. In this paper, he gives an alternate proof that $\mu=0$ for abelian number ...
1 vote
1 answer
215 views

A confusion about power series and p-adic measures

In page 16 of these notes on $p$-adic $L$-functions, it makes the following claim: Let $\alpha$ be a $p$-adic measure on $\mathbf{Z}_p$ which corresponds to a power series $F_{\alpha}(T) \in \mathbf{...
5 votes
1 answer
144 views

Describing the Gamma-transform explicitly in terms of power series

The Gamma transform of a measure is defined as follows. If $\alpha$ is a $\mathbf{Z}_p$-valued measure on $\mathbf{Z}_p$, then the Gamma transform of $\alpha$ is: $$\Gamma_{\alpha}(s) = \int_{\mathbf{...
4 votes
0 answers
140 views

Alternative formulation of the Ferrero-Washington Theorem

The Ferrero-Washington theorem says that if $K/\mathbf{Q}$ is an abelian extension, then the cyclotomic $\mathbf{Z}_p$ extension $K^{\text{cyc}}/K$ has $\mu=0$. In the paper "Iwasawa invariants ...
3 votes
1 answer
223 views

What's the class group of $\mathbb{Q}^{\mathrm{ab}}$?

If $K/\mathbb{Q}$ is an infinite algebraic extension, define as usual the class group $Cl_K$ by the direct limit via the natural (conorm) map $Cl_K := \lim\limits_{\rightarrow} Cl_F$, where $F$ runs ...
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4 votes
0 answers
218 views

The Gamma-transform and $p$-adic $L$-functions

I'm currently reading the paper "On the $\mu$-invariant of the $\Gamma$-transform of a rational function" by W Sinnott. In this paper, he gives an alternate proof that $\mu=0$ for abelian ...
2 votes
1 answer
117 views

Studying a connection between Iwasawa theory and the $K(n)$-local Picard group by some geometry on the Lubin-Tate stack

Let $Pic_n^0$ denote the even part of the $K(n)$-local Picard group, and let $Pic_n^*$ denote $Hom(Pic_n^0, W(\mathbb{F}_{p^n})^x)$. Denote by $L$ the profinite group ring $\mathbb{Z}_p[[Pic_n^*]] $. ...
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2 votes
1 answer
91 views

Mordell-Weil rank growth in Iwasawa tower

This is more of a reference request in case anyone can direct me to the right literature. I asked originally on MathStack, but I was suggested to better post it here. If you have an elliptic curve $E/\...
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4 votes
1 answer
167 views

Order of $37$-Sylow subgroup of ideal class group of $K_{37} = \Bbb Q(\mu_{37^{n}})$ is known to be $37^n$

I want to examine nontrivial examples of what we call Iwasawa class formula, $c(n)=\mu p^n + \lambda n + \nu$, where $\lambda, \mu \in \mathbf N$ and $\nu \in \mathbf Z$ are parameters depending only ...
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2 votes
1 answer
126 views

Finding a certain value of $\Gamma_p$

Let $\Gamma_p : \mathbb{Z}_p \to \mathbb{Z}_p^{\times}$ be the $p$-adic gamma function. I thought that I had successfully calculated $\Gamma_p(1 - 1/4)$, but sage is telling me I'm wrong (this is ...
2 votes
2 answers
157 views

Value of the quadratic Gauss sum viewed in $\mathbb{C}_p$

Let $p > 2$ be a prime and $q = p^r$ for some $r \in \mathbb{Z}^+$. I will assume that all roots of unity lie in $\mathbb{C}_p^{\times}$. Let $\zeta$ a primitive $p$-th root of unity. Let $Tr : ...
5 votes
1 answer
207 views

Non-commutative knot invariants

$\newcommand{\ab}{\mathrm{ab}}$Let $L=K_1\cup \dots \cup K_r$ be a link embedded in a 3-sphere. Here, $K_1,\dots, K_r$ are the component knots of $L$. A prototypical invariant associated with $L$ is ...
2 votes
0 answers
70 views

Question about infinitude of $m$-irregular primes

Let $p>2$ be a prime, $\zeta$ a primitive $p$th root of unity, and $m >0$ a square-free integer such that $m \not\equiv 3 \mod 4$ and $\gcd(m,p)=1$. Let $\chi$ be the imaginary quadratic ...
2 votes
1 answer
107 views

Does $\mu=0$ for an imaginary quadratic field $K$ imply $\mu=0$ for $\mathbf{Q}$?

Suppose that $E/\mathbf{Q}$ is an elliptic curve and $K$ is an imaginary quadratic field. Let $\mathbf{Q}_{\infty}$ denote the cyclotomic $\mathbf{Z}_p$ extension of $\mathbf{Q}$, and let $K_{\infty}$ ...
3 votes
0 answers
127 views

Relationship between fine Selmer groups and class groups

Given an elliptic curve $E_{/\mathbb{Q}}$ and an odd prime number $p$, let $S$ be the set of primes consisting of $p$ and the primes at which $E$ has bad reduction. The fine Selmer group $R_{p^\infty}(...
2 votes
1 answer
197 views

Calculating the Galois cohomology group $H^1(K_v, \, E[p^{\infty}])$

Suppose $K$ is a number field and $E$ is an elliptic curve defined over $K$. My question is: how do you compute the local cohomology group $H^1(K_v, \, E[p^{\infty}])$? As to why I'm asking this, it ...
2 votes
1 answer
106 views

Structure theorem for finitely generated $\Lambda$-modules - uniqueness part

In Iwasawa theory, one of the fundamental results is the following structure theorem for finitely generated modules over the ring $\Lambda = \mathbf{Z}_p[[T]]$. If $M$ is a finitely generated torsion ...
5 votes
0 answers
83 views

Structure of finitely generated $\mathbb{Z}/p^n\mathbb{Z}[[S,T]]$-modules

Let $\Omega=\mathbb{Z}/p\mathbb{Z}[[S,T]]$. $\Omega$ is a commutative, Noetherian and integrally closed domain of Krull dimension 2. According to Bourbaki's commutative algebra VII $\S 4$, if $M$ is a ...
3 votes
0 answers
112 views

What do congruences between modular forms tell us about $\mu$-invariants of elliptic curves?

This question is based off these notes by Preston Wake about Iwasawa invariants and Hida Families. In the notes, the author asks "why" the elliptic curve $11A3$ has $\mu$-invariant equal to $...
1 vote
1 answer
223 views

Classification of cyclotomic fields with class number 1

1.Let $p$ be an odd prime number. Is there a classification of cyclotomic fields of the form $\mathbb{Q}(\zeta_p)$ with class number 1? 2.Is there such a classification for general cyclotomic fields $...
2 votes
0 answers
131 views

Has there been much research on the Iwasawa theory of bi-quadratic fields?

The simplest non-trivial example of $\mathbb{Z}_p$-extensions happen over imaginary quadratic fields and I've seen a good amount of research done here (from my understanding still a lot to learn). I ...
22 votes
1 answer
767 views

Why is the regulator of the degree 11 extension of $\mathbb{Q}$ so large?

Let $K_\infty/\mathbb{Q}$ denote the $\hat{\mathbb{Z}}$-extension of $\mathbb{Q}$. Then for each $n\geq1$, $K_\infty$ has a unique subfield $K_n$ of degree $n$ over $\mathbb{Q}$. The fields $K_n$ are ...
6 votes
1 answer
339 views

How hard is it to find the first layer of this basic $\mathbb{Z}_p$-extension?

Let $p$ be a prime number and $\zeta_{p^n}$ be a primitive $p^n$-th root of unity. We know that there is a unique subfield $\mathbb{Q}_1$ of $\mathbb{Q}(\zeta_{p^2})$ such that $[\mathbb{Q}_1:\mathbb{...
3 votes
0 answers
115 views

Average size of class groups of cyclotomic fields: three perspectives

Let $K$ be a number field. Let $h(K)$ denote the class number (i.e., the size of the ideal class group) of $K$, $R(K)$ be the regulator of $K$, and $\Delta_K$ the discriminant of $K$. Let $\mathcal{F}$...
2 votes
1 answer
120 views

Existence of non-zero pseudo-null submodules

Let $p$ be a rational prime, and let $\Lambda_d$ be the Iwasawa algebra in $d$ variables, i.e. $\Lambda_d = \mathbb{Z}_p[[T_1, \ldots, T_d]]$. Let $A$ be a finitely generated and torsion $\Lambda_d$-...
2 votes
0 answers
105 views

Iwasawa theory over function fields - How do eigenvalues vary in $\mathbb Z_\ell$ towers?

Consider a tower of curves $\dots \to C_n \to C_{n-1} \dots \to C_1$ over $\mathbb F_q$ where $C_n: f(x^{\ell^n},y) = 0$.We can look at the multiset $S_n$ of eigenvalues of the Frobenius $\sigma_q$ on ...
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3 votes
0 answers
141 views

Finiteness of points over the cyclotomic extension for modular forms

Let $\rho(f):G_\mathbb{Q} \rightarrow GL_2(K_f)$ be the Galois representation attached to some cuspidal modular form $f$ where $K_f$ is a finite extension of $\mathbb{Q}_p$. Let $V_f$ be the vector ...
2 votes
0 answers
90 views

Iwasawa's results about relation between Galois cohomology and principal factorization

Let $K$ be a Galois number field with Galois group and units group $G$ and $U$, respectively. How we can relate the first cohomology group $H^1(G,U)$ to principal factorization in K? I'd try to find ...
2 votes
0 answers
173 views

Merel's theorem on uniform bound for torsion of all elliptic curves

I am reading Silverman's book on Arithmetic of elliptic curves. There he mentions a theorem of Merel (Thm 7.5.1) which reads like this. Thm: For every integer $d \geq 1$, there is a constant $N(d)$ ...
2 votes
0 answers
145 views

Tate module of elliptic curves; Commuting Hom functor and tensor product in the second coordinate

Let $\Lambda$ be the Iwasawa Algebra of the Galois group of the cyclotomic $\mathbb{Z}_p$-extension $\mathbb{Q}_{cyc}$ of $\mathbb{Q}$. Let $\widehat{\Lambda}$ be its Pontryagin dual (i.e the ...
2 votes
0 answers
81 views

Elementary Iwasawa module

Let $k$ be a given number field. What is the importance and applications of knowing that the Iwasawa module $X_\infty$ of $k$ is an elementary $\Lambda$-module?
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5 votes
1 answer
252 views

Classification of finitely generated modules over non-commutative rings

Let $\Lambda$ be a commutative integral ring with an automorphism $\sigma$ (I have in mind $\mathbb Z_p[[t]]$ and $\sigma(t) = (1+t)^\alpha - 1$ with $\alpha \in \Lambda^\times$) and $R = \Lambda\{F\}$...
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4 votes
1 answer
131 views

Completely split primes in non-anticyclotomic $\mathbb{Z}_p$-extensions

In his colloquium paper "The Structure of Selmer Groups" Greenberg writes the following: If $K$ is an imaginary quadratic field ... it is conjectured that for any [non-anticyclotomic] $\mathbb{Z}_p$...
2 votes
0 answers
78 views

Regular growth of ranks in Iwasawa tower

$\newcommand{\rank}{\operatorname{rank}}$Let $G=H \times K$ be a torsion free pro-$p$, $p$-adic Lie group. Let $H =\mathbb{Z}_p$, the ring of $p$-adic integers and $K$ is a non-commutative torsion ...
1 vote
1 answer
235 views

Completed cohomology and variants

I am interested in the following set up: I have an ind-sequence of curves $\dots X_2\to X_1$ defined over a finite field of characteristic $p$ such that $X_n/X_{n-1}$ is a Galois degree $\ell$ cover ...
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8 votes
1 answer
479 views

Why can Euler systems constructed from algebraic cycles only be anticyclotomic?

In a footnote to the 2018 Zerbes-Loeffler lecture notes from the Arizona Winter School, it's stated that Euler systems constructed from algebraic cycles "cannot give a full Euler system, only an ...
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5 votes
1 answer
251 views

Adjoint Selmer groups and Deformation rings

Let $\rho:\operatorname{Gal}(\bar{\mathbb{Q}}/\mathbb{Q})\rightarrow \operatorname{GL}_2(\bar{\mathbb{Z}}_p)$ be a $p$-adic Galois representation associated to a $p$-ordinary Hecke eigencuspform, let $...
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2 votes
1 answer
210 views

Modular symbols associated to Rankin Selberg convolutions and the symmetric square

I'm interested in understanding how one may associate modular symbols to the L-functions and $p$-adic L-functions associated to the Rankin Selberg convolution of two modular forms/ elliptic curves and ...
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2 votes
1 answer
251 views

Generalized Greenberg's conjecture for imaginary quadratic fields

Let $K$ be an imaginary quadratic field and $\widetilde{K}$ be the compositum of all $\mathbb{Z}_p$ extensions of $K$. Here, $\widetilde{K}/K$ is a $\mathbb{Z}_p^2$ extension. Define $M(\widetilde{K})$...
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2 votes
1 answer
183 views

Euler characteristics in the rank one case

Suppose $E$ is an elliptic curve over a number field with good ordinary reduction at the primes above a fixed odd prime $p$. We are interested in the Iwasawa theory over the cyclotomic $\mathbb{Z}_p$ ...
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4 votes
0 answers
129 views

Is there a converse to Vatsal's theorem on congruence of p-adic L-functions?

Let $f=\sum_n a_n(f) q^n$ and $g=\sum_n a_n(g) q^n$ be normalized (cuspidal) newforms whose Fourier coefficients are contained in the p-adic field K for which the uniformizer of $\mathcal{O}_K$ is ...
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1 vote
0 answers
90 views

Existence of nontrivial finite sub-modules in the cyclotomic extension

It is a well established fact (by Greenberg) that if $p$ is a prime of good ordinary reduction of an elliptic curve $E/\mathbb{Q}$, then the dual of the Selmer group, denoted by $X(E/\mathbb{Q}_{cyc})$...
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1 vote
0 answers
95 views

Trivial fine Selmer group in the cyclotomic extension

In explicit examples that I have seen worked out, it appears that when the fine Selmer group is finite in the cyclotomic extension it is in fact trivial. Is there any reason to expect that this ...
  • 1,079
10 votes
1 answer
884 views

Iwasawa theory and perfectoid spaces

Have there been any applications of perfectoid theory to Iwasawa theory? At a first glance, this seems like a natural choice. For instance, the field $\mathbb Q_p(\mu_p^{1/p^\infty})$ is studied in ...
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3 votes
1 answer
385 views

State of the art on the main conjecture for supersingular elliptic curves/modular forms

Kobayashi formulated the analog of the main conjecture in Iwasawa's theory for elliptic curves which are supersingular at a prime p. This makes use of the $\pm$ Selmer groups which are shown to be ...
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1 vote
0 answers
53 views

Infinite Non Abelian Extensions Unramified Outside p

Let $K$ be a number field and $p$ be a fixed odd prime. Suppose $\mathfrak{p}\mid p$ is the only prime prime above $p$ in $K$, and that $p$ does not divide the class number of $K$ (I am okay with ...
  • 1,079
6 votes
0 answers
142 views

$\lambda$-invariants in cyclotomic $\mathbb{Z}_p$ extensions

The idea that Selmer groups and class groups are related is not new. More recently, we understand that the growth patterns of fine Selmer groups are very similar to that of class groups in cyclotomic $...
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