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An elliptic curve is an algebraic curve of genus one with some additional properties. Questions with this tag will often have the top-level tags nt.number-theory or ag.algebraic-geometry. Note also the tag arithmetic-geometry as well as some related tags such as rational-points, abelian-varieties, heights. Please do not use this tag for questions related to ellipses; instead use conic-sections.

4 votes

Finiteness and bounds for elliptic curves realizing a given galois representation

The set $\mathcal{L}_{\rho}$ is either empty, or a singleton finite. This follows from Faltings' isogeny theorem, which states that for any two elliptic curves (or, more generally, abelian varieties) …
David Loeffler's user avatar
6 votes
Accepted

Evidence for the equivariant BSD conjecture with higher multiplicity

You might want to study the work of Darmon--Lauder--Rotger, notably this paper: https://web.mat.upc.edu/victor.rotger/docs/DLR1.pdf They study cases of the equivariant BSD conjecture where $\rho$ is a …
David Loeffler's user avatar
10 votes
Accepted

Definition of modular curve associated to $\Gamma(N)$

This is a subtle issue (which has come up before on this site several times, see e.g. is the modular curve X(N) defined over Q? for a related question). Your $S(N)$ is naturally a scheme over $\mathbb …
David Loeffler's user avatar
2 votes
Accepted

Why does $[I](P)=0$ ($P\in E$) imply $[\psi(I)](P)=0$ ? ($\psi$ is Hecke character of ellipt...

This is essentially the same as your other recent CM-theory question, in a mild disguise; for both questions the point is that $\psi(I)$ is a generator of $I$. This follows easily from the fact that $ …
David Loeffler's user avatar
9 votes
Accepted

Non-modular elliptic curves

It is a widely believed conjecture that all elliptic curves, over any number field $K$, are modular (in the sense that there exists an automorphic representation [*] $\pi$ of $\operatorname{GL}_2 / K$ …
David Loeffler's user avatar
11 votes
Accepted

Do there exist elliptic curves over $H_K$ having everywhere good reduction and CM by $\mathc...

Here is an example. Let $K = \mathbf{Q}(\sqrt{-21})$. Then the class group of $K$ is $C_2 \times C_2$ and its Hilbert class field is $H_K = \mathbf{Q}(\sqrt{-1}, \sqrt{3}, \sqrt{7})$. In particular, $ …
David Loeffler's user avatar
4 votes
Accepted

Rationalizing and minimizing elliptic curve coefficients

If I understand correctly: you are starting with $a = 10656\sqrt{-23} +13600$, and you want to choose $f$ in the same number field such that $af^2$ is "as nice as possible", ideally lying in $\mathbf{ …
David Loeffler's user avatar
5 votes

Frobenius actions on de Rham cohomology of ordinary elliptic curves

It's important to be clear that this map on $H^1_{\mathrm{dR}}$ overlies a highly non-trivial map on the base-ring $R$. You can imagine a case where $R$ is something like $\mathbf{Z}_p\langle X \rangl …
David Loeffler's user avatar
7 votes
Accepted

Global section of vertical differential 1 forms on universal elliptic curve

What you're looking for is a section of the sheaf $\omega = \pi_* \Omega^1_{E/B}$, where $\pi: E \to B$ is the structure map, which is a line bundle on $B$. This line bundle $\omega$ has a canonical …
David Loeffler's user avatar
23 votes
Accepted

Quaternionic and octonionic analogues of the Basel problem

This isn't really a full answer, but it's too long for a comment, and perhaps it's informative all the same. Your sum $S_k[\mathcal{O}]$ can be written as the value at $s = k$ of the sum $$\sum_{0 \ne …
David Loeffler's user avatar
9 votes
2 answers
715 views

Q-curves and twisting

An elliptic curve $E$ over $\overline{\mathbb{Q}}$ is called a $\mathbb{Q}$-curve if it is isogenous (over $\overline{\mathbb{Q}}$) to all its Galois conjugates -- see Are Q-curves now known to be mod …
David Loeffler's user avatar
4 votes
Accepted

Modular symbols associated to Rankin Selberg convolutions and the symmetric square

I do not think there is a reference for this theory, because as far as I know no such theory exists. I have spent a substantial portion of my career studying the arithmetic of the special values of th …
David Loeffler's user avatar
5 votes
Accepted

Vanishing of L-function of elliptic curve over $\mathbb{Q}$

Just to pick up on something mentioned in @MyNinthAccount's answer: If you just want to determine whether or not $L(E, 1) = 0$, then there is another approach, which doesn't involve computing $L(E, …
David Loeffler's user avatar
6 votes
Accepted

Existence of newforms which are non-ordinary at a given prime

Given p and k, it's clear we can find a CM-type newform of weight k and some level which is supersingular at p (just choose an imaginary quadratic field in which p is inert, and some sufficiently larg …
David Loeffler's user avatar
14 votes
Accepted

BSD conjecture for rank 1 elliptic curves

The following theorem is due to Chris Skinner, in this 2014 paper. Let E/Q be an elliptic curve such that rank E(Q) = 1 and the Tate-Shafarevich group Sha(E / Q) is finite, and some other techni …
David Loeffler's user avatar

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