# Tagged Questions

**5**

votes

**2**answers

185 views

### Why is the supersingular locus the zero locus of a modular form?

This question is related to my other question here: Examples of subspaces singled out by modular forms.
Here I am wondering if there is a philosophical explanation about why the supersingular locus ...

**1**

vote

**0**answers

69 views

### The minimum genus of a family of degree $12$ algebraic curves which comes from the resultant of two quartic polynomials

Let $f(t)$ be a rational normal cubic curve in $\mathbb{P}^3$ (it is not contained in any plane) and also we assume that this cubic curve passes through two points $(0,0,0)$ and $(1,0,0)$. By an easy ...

**0**

votes

**0**answers

422 views

### A letter from J. P. Serre

Which is the letter where J. P. Serre present "Analogues Kählériens de certaines conjectures de Weil" to Weil?

**4**

votes

**2**answers

282 views

### Time-line until the publicaton of Weil of “Numbers of solutions of equations in finite fields”

In "On the history of the Weil Conjectures" Dieudonné says:
"Appropriately enough, the story, as with so many problems in number theory, begins with Gauss...".
C. F. Gauss, Disquisitiones ...

**5**

votes

**1**answer

299 views

### Connection of Galois representation and arithmetic geometry

This is might be a dumb question. There are lots of Galois representations which arise naturally from geometric objects, for example, Galois representations attached to elliptic curves. I know that ...

**1**

vote

**0**answers

208 views

### Where can I find the article of A. Borel: “Values of zeta-functions at integers, cohomology and polylogarithms”? [closed]

Where on the internet can I find this article?
I know that it is in this book: Current trends in mathematics and physics, Narosa, New Delhi, 1995.

**19**

votes

**2**answers

1k views

### Interactions between (set theory, model theory) and (algebraic geometry, algebraic number theory ,…)

Set theory and model theory have many applications outside of logic, in particular in algebra, topology, analysis, ...
On the other hand model theory, in particular after Hrushovski, found many ...

**1**

vote

**1**answer

190 views

### Arithmetic property of a surface of general type

In my previous post I asked about the hyperbolicity of the affine surface $S'=\{zw \neq o\}$ in the projective surface $z^2 = P(x) Q(y)$ in $\mathbb{P}^3$, where $P$ and $Q$ are two general ...

**3**

votes

**3**answers

488 views

### Non existence of cyclic infinite linear algebraic groups

Let $G$ be a linear algebraic group defined over some algebraically closed field $\mathbb{K}$ and also over some subfield $k\subset \mathbb{K}$. There is thus a natural group structure on the set of ...

**4**

votes

**0**answers

135 views

### Continuity of the Hilbert pairing

I would like to know if the Kummer pairing (or the analogue of the Hilbert Symbol) for a one dimensional group defined over the ring of integers of a higher-dimensional local field is continuous (with ...

**11**

votes

**4**answers

503 views

### Analogy between the nodal cubic curve $y^2=x^3+x^2$ and the ring $\mathbb{Z}[\sqrt{-3}]$?

I'm trying to motivate a bit of algebraic geometry in an abstract algebra course (while simultaneously trying to learn a bit of algebraic geometry), and I thought that it might be nice to present an ...

**2**

votes

**1**answer

250 views

### Mordell-Weil and finiteness of rational points

Let $E$ be a CM elliptic curve defined over a quadratic imaginary field $K$ with maximal order, that is, $\mathrm{End}_K(E)\cong \mathcal{O}_K$. Suppose the class number of $K$ is equal to $1$. Let ...

**2**

votes

**0**answers

151 views

### Lang's preprint “Cyclotomic points, very anti-canonical varieties, and quasi-algebraic closure”

I am trying to find the following preprint of Serge Lang, which supposedly discusses his C1 conjecture:
"Cyclotomic points, very anti-canonical varieties, and quasi-algebraic closure".
I have not ...

**1**

vote

**1**answer

223 views

### Rational points of non-rational curves

An algebraic curve (in this question) is the zero set $C = f^{-1}(X\ Y)$ of any polynomial $f\in\mathbb R[X\ Y]$; we say then that $f$ represents $C$. ...

**1**

vote

**0**answers

108 views

### Isogenies in multidimensional formal groups

Let $K/\mathbb{Q}_p$ be a local field, $A$ the ring of integers of K, $\pi$ a uniformizer element for $A$, $F$ an n-dimensional formal group with coefficients in $A$ and $f$ an endomorphism of $F$. ...

**3**

votes

**1**answer

203 views

### Modular Functions with Rational Fourier Expansions

I have been reading the paper of Cox, McKay and Stevenhagen "Principal Moduli and Class Fields", http://arxiv.org/pdf/math/0311202v1.pdf, and I have a question regarding the nature of the function ...

**3**

votes

**1**answer

123 views

### How to estimate a local hilbert samuel funcion

Let $X$ be a reduced hypersurface in the projective variety $\mathbb{P}^n(K)$, where $K$ is a number field. Select $\xi$ is a $F_{\mathfrak{p}}$-rational point of $X$ where $\mathfrak{p}$ is a prime ...

**5**

votes

**1**answer

433 views

### Analogy between Jacobian of curve and Ideal class group

It is excerpt from "Algebraic Geometry Codes Basic ...

**10**

votes

**1**answer

939 views

### Are overlaps among {algebraic geometry, arithmetic geometry, algebraic number theory} growing?

From a naive outsider's viewpoint, just watching the MO postings
in those three fields scroll by, and hearing of breakthroughs in the news,
it appears there might be increasing overlap among the ...

**16**

votes

**1**answer

449 views

### Is there a known example of a curve X of genus > 1 over Q such that we know the number of points of X over the n-th cyclotomic field, for every n?

By Falting's theorem, these numbers are of course finite. Is there an example where we can explicitly compute them for every $n$?
Thank you!

**1**

vote

**0**answers

84 views

### points in $V(\bar K \otimes_{\bar Q} \bar L)$ rational over tensor product of fields

Let V be a variety over a number field, and let K and L be two algebraically closed
What is known about the points of $V(\bar K \otimes_{\bar Q} \bar L )$ ?
Are there results claiming that points in ...

**3**

votes

**0**answers

118 views

### P-adic Weierstrass Lemma for several variables

The p-adic Weiestrass lemma asserts that a power series $f(z)$ with coefficients in the ring of integers of a local field can be factored as $π^n·u(z)·p(z)$ where u(z) is a unit in the ring of power ...

**14**

votes

**1**answer

707 views

### Principal maximal ideals in Z[x]/(F)

Is there some irreducible $F \in \mathbb{Z}[x]$ such that $\mathbb{Z}[x]/(F)$ has no principal maximal ideal? Equivalently, is it possible that the $1$-dimensional integral domain $\mathbb{Z}[x]/(F)$ ...

**6**

votes

**1**answer

306 views

### Rational points on surfaces of general type

The weak Lang conjecture asserts that rational points on a variety of general type defined over $\mathbb{Q}$ are not Zariski dense (same replacing $\mathbb{Q}$ with a number field). This one is proved ...

**1**

vote

**1**answer

193 views

### Functional equations of zeta functions over global fields

The functional equations for Dedekind zeta functions (zeta functions attached to rings of integers in algebraic number fields) come from functional equations of theta functions like $\sum_{n \in ...

**2**

votes

**1**answer

166 views

### An expression for the function $f_e$ that appears in the Weil Pairing

Let $K$ be a local field and $E/K$ an elliptic curve such that the set of $N$-torsion points, $E[N]$, is contained in $E(K)$. For $e$ in $E[N]$, I am interested in finding and expression for the ...

**4**

votes

**3**answers

402 views

### Orders of Number Fields

Let $K$ be a number field over $\mathbb{Q}$ of degree $n$, and $\mathcal{O} \subset \mathcal{O}_K$ an order.
$\textbf{Questions:}$
$\newcommand{\Spec}{\textrm{Spec }}$
$\newcommand{\cO}{\mathcal{O}}$
...

**6**

votes

**2**answers

403 views

### Jacobians defined over smaller fields

Let $L/K$ be an extension of number fields.
Let $X$ be a curve over $L$ which can not be defined over $K$. Let $J(X)$ be the Jacobian of $X$ over $L$.
In general, the Jacobian $J(X)$ probably ...

**6**

votes

**1**answer

642 views

### $\ell$-adic Weil cohomology theory

I have a reference or counterexample request. Suppose $k$ is a field and $\ell\neq char(k)$. There are several common references that show that $H^i_{et}(-, \mathbb{Q}_\ell )$ is a Weil cohomology ...

**2**

votes

**3**answers

661 views

### Are all Finite Subsets of Affine n-space Algebraic sets, and related question [closed]

For an algebraicaly closed field $k$ are all finite subsets of Affine $n$-space $A^{n}\left(k\right)$
algebraic sets (here for $n>1$), and if so, for a given finite set $X\subset ...

**4**

votes

**0**answers

264 views

### What is the shape of the zeta function of a singular hypersurface?

So let $X$ be a projective hypersurface inside $\mathbb{P}_{\mathbb{Z}}^n$ of degree $d$.
Assume that
(a) $X(\mathbb{C})$ and $X(\overline{\mathbb{F}}_p)$ are irreducible,
(b) and that ...

**1**

vote

**1**answer

298 views

### Centralizer of elliptic elements in $GL(2)$

Consider a global field $F$ and the group $\Gamma =GL(2,F)$. An element $\gamma \in \Gamma$ is called elliptic, if its eigenvalues do not lie in $F$. Now consider a completion $F_v$ of $F$ and $G_v = ...

**0**

votes

**3**answers

1k views

### Where Can i find the lecture Videos of BSD 2011

i recently heard that there was a conference on Birch and Swinnerton dyer conjecture Held at Cambridge on May 4 until May 6,
the main theme is "The conference marks the 50th anniversary of the ...

**28**

votes

**3**answers

2k views

### On what kind of objects do the Galois groups act?

I am neither number theorist nor algebraic geometer. I am wondering
whether Galois groups of number fields (say the absolute Galois
group $Gal(\overline{\mathbb{Q}}/\mathbb{Q})$) act on objects which
...

**2**

votes

**1**answer

463 views

### Endomorphism ring of the adeles and ideles?

What are the (cont.) endomorphisms resp. automorphisms of the adeles (for a given global field)
1) as a topological abelian group and
2) as a topological ring?
3) What are the endomorphisms and the ...

**13**

votes

**4**answers

2k views

### Conceptualizing Weil Pairing for elliptic curves ( and number fields)

There are two explanations in Silverman ( Arithmetic of Elliptic Curves), one in exercises developing the Weil reciprocity law ( for algebraic curves) and then generalizing, and then there is a ...

**7**

votes

**1**answer

753 views

### Parametrization of 2-dimensional torus

The units with norm $+1$ in a pure cubic number field $K$ generated
by a cube root of $m = ab^2$, where $a$ and $b$ are coprime and
squarefree integers, correspond to integral points on the torus
$$ ...

**19**

votes

**1**answer

944 views

### Weil Conjectures for Number Fields

Let $K$ be a number field with integral basis $\{\omega_1,\ldots,\omega_n\}$.
The affine variety $A_K$ defined by
$$ N_{K/\{\mathbb Q}}(X_1 \omega_1 + \ldots + X_n \omega_n) = 1 $$
is an algebraic ...

**5**

votes

**1**answer

239 views

### Parametrization of unit varieties

Let $K$ be a number field with integral basis $\{\omega_1,\ldots,\omega_n\}$. Then
$$ \Phi(X_1, \ldots, X_n) = N_{K/{\mathbb Q}}(\omega_1 X_1 + \ldots + \omega_n X_n) $$
is a homogeneous polynomial of ...

**2**

votes

**1**answer

638 views

### A unique zero of a system of polynomials is a zero of a finite system.

Suppose $p$ is a point in $\mathbb{R}^n$ so that among the set $S$ of polynomials in $\mathbb{Z}[x_1,\ldots,x_n]$ which equal zero at $p$, $p$ is the only point in some neighborhood of $p$ at which ...

**5**

votes

**2**answers

1k views

### Is there a Riemann-Roch for smooth projective curves over an arbitrary field?

Let $X$ be a smooth projective curve over a field $k$. We let $\omega$ be the canonical
line bundle of $X$ and we denote by $F$ the field of $k$-valued rational functions on $X$.
(1) When $k$ is ...

**12**

votes

**3**answers

638 views

### Frobenius elements from the point of view of étale fundamental groups

The goal of this question is to find a "geometric" definition of Frobenius element in $\text{Gal}(\overline{\mathbb{Q}}/\mathbb{Q})$.
Here are two definitions that don't work, but that should help ...

**6**

votes

**2**answers

754 views

### “Bad” reduction of Shimura curves via dual graphs

I have the following naive (and inexpert) question about the
reduction of Shimura curves at primes dividing the discriminant
of the underlying quaternion algebra. It requires some background
to ...

**4**

votes

**0**answers

266 views

### What to call the following variant of tame ramification

Suppose that $R \subseteq S$ is a generically separable extension of 1-dimensional normal domains (you can assume that $R$ is local if you'd like) of equal-characteristic $p > 0$ (for simplicity, ...

**5**

votes

**4**answers

2k views

### Elliptic curves over finite fields

I have basic questions about elliptic curves over finite fields.
Where to find general references? Hartshorne for instance restricts to algebraically closed ground fields.
Over an arbitrary field ...

**3**

votes

**1**answer

683 views

### How do I visualize finite covers of curves over non-algebraically closed fields?

If $L$ is algebraically closed, fields of transcendence degree one over $L$ correspond to algebraic curves over $L$ up to birational equivalence, and finite extensions correspond to finite Galois ...

**14**

votes

**4**answers

731 views

### Etale coverings of certain open subschemes in Spec O_K

Although my number theory is really weak, I'm trying to understand the notion of etale coverings in this context. I think this could provide a very interesting point of view.
Let $U$ be an open ...

**4**

votes

**1**answer

644 views

### 2d Weil conjecture

Does there exist a two variable analogue of the Weil conjecture?
What I mean is that the usual Weil involves a one-variable zeta-function which you get by using numbers $V_n = V ( GF(p^n))$ of points ...

**6**

votes

**1**answer

444 views

### Can algebraic number fields be generalized in a similar way to function fields in 1 variable over a finite field?

Global fields consist of finite extensions of $\mathbb{Q}$ (algebraic number fields) and finite extensions of $\mathbb{F}_q(x)$ (function fields in 1 variable over a finite field). The latter are ...

**13**

votes

**1**answer

479 views

### components of E[p], E universal in char p.

I have just realised that a group scheme I've known and loved for years is probably a bit wackier than I'd realised.
In this question, in Charles Rezk's answer, I erroneously claim that his ...