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Prime numbers, diophantine equations, diophantine approximations, analytic or algebraic number theory, arithmetic geometry, Galois theory, transcendental number theory, continued fractions

2 votes

Class number formula for binary hermitian forms

May be you can consult Latimer's paper On ideals in generalized quaternion algebras and Hermitian forms., Trans. Amer. Math. Soc. 38 (1935), no. 3, 436–446. The main theorem (Theorem 3) establishes …
Filippo Alberto Edoardo's user avatar
7 votes
Accepted

A question on Iwasawa theory

By Theorem 13.31 in L. Washington Introduction to Cyclotomic Fields, Second Edition, GTM 83 we know that $\mathcal{X}\sim \Lambda^{r_2}\oplus(\Lambda-$torsion), where $r_2$ is the number of complex em …
Filippo Alberto Edoardo's user avatar
3 votes
Accepted

Fourier expansions in function fields

Yes, there is and is called $t$-expansion rather than $q$-expansion - may be, though, you might want to replace your $\Omega$ by $$ \widehat{\bar{K_\infty}}\setminus K_\infty $$ where I denote by $K_\ …
Filippo Alberto Edoardo's user avatar
2 votes
Accepted

Cohomology of a group with a topological generator

Well, if you consider the definition of cohomology, you see that $H^0(N_0,V)$ are the fixed point, namely $v\in V$ such that $gv=v$ for all $g\in N_0$ (which, I suppose, is your group). If the group w …
Filippo Alberto Edoardo's user avatar
1 vote

N-coinvariants of $\mathcal{C}^{sm}_c(N,A)$ (compactly supported smooth functions on $N$) ?

My answer is just a detailed version of David Loeffler's comment. First of all, I would observe that $N\cong \mathbb{Q}_p$ via $$ \left( \begin{array}{cc} 1&a\\ 0&1 \end{array}\right)\mapsto a $$ Mor …
Filippo Alberto Edoardo's user avatar
2 votes
Accepted

Does the Hasse norm theorem easily imply the global squares theorem?

Well, I would say that this crucially depends on what you define to be "quick". If you admit global class field theory, at least in its idelic formulation, the fact that all primes in $K$ are split in …
Filippo Alberto Edoardo's user avatar
2 votes
Accepted

Kummer theory isomorphism and Kummer extensions

Well, let me try in an elementary way. Pick any field $K$ of characteristic prime to $p$ and suppose it does not contain any $p^n$-th root of unity. Let $a\in K^\times\setminus (K^\times)^p$. Then, th …
Filippo Alberto Edoardo's user avatar
5 votes
Accepted

Tate's thesis for varieties over finite fields

This is done in Chapter 7.3 of Ramakrishnan and Valenza's Fourier Analysis on Number Fields (GTM 186) which, despite the title, describes in some details also the situation over function fields in one …
Filippo Alberto Edoardo's user avatar
3 votes

Computing certain class numbers modulo 4

I come later than GH and paul Monsky and with an intricate and way too long answer, but since I had fun in solving the exercice, I post it anyhow. Most probably (as paul Monsky suggested) there are ea …
Filippo Alberto Edoardo's user avatar
2 votes

the first cohomology group of units of biquadratic number fields

Following Felipe's answer, I would like to suggest a slightly different strategy which makes deep use of your very peculiar setting (and probably boils down to Felipe's advise). Warning: At the very e …
Filippo Alberto Edoardo's user avatar
3 votes

Leopoldt's conjecture and cup-products

I think your cup-product is always zero independently of Leopoldt (at least if $\chi$ is of finite order). Consider $\mathbb{Z}_p$-coefficients instead (enough by Neukirch-Schmidt-Wingberg, 2.3.10). I …
Filippo Alberto Edoardo's user avatar
3 votes

class numbers of $\mathbf{Q}(2^{1/n})$

As KConrad says, the answer to the first question is "not yet known". For Iwasawa theory, you could consider the extension $L_\infty=\mathbb{Q}(\sqrt[p^\infty]{2},\zeta_{p^\infty})$ which is Galois ov …
Filippo Alberto Edoardo's user avatar
3 votes
Accepted

Elements of absolute value 1 in cyclotomic extension of dyadic rationals

The answer is yes. Let $K=\mathbb{Q}(\zeta)$ and suppose that there is an element $u\in\mathbb{Z}[\frac{1}{2},\zeta]$ such that for some embedding $\sigma_0\colon K\hookrightarrow \mathbb{C}$ the abso …
Filippo Alberto Edoardo's user avatar
5 votes
Accepted

Are Galois groups of Q with restricted ramification supposed to be finitely generated?

I think you can look at page 532 of (the first version of) J. Neukirch, A. Schmidt, K. Wingberg, Cohomology of Number Fields, Springer, 1999. They explicitly write that we do not even know precisely w …
Filippo Alberto Edoardo's user avatar
10 votes

von Staudt-Clausen for other special values

The von Staudt-Clausen theorem indeed asserts that the denominators of Bernoulli numbers have special behaviour, but from a modern perspective what is even deeper are the so-called Kummer's congruenc …
Filippo Alberto Edoardo's user avatar

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