Questions tagged [complex-multiplication]

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What's the dimension of the space of CM cusp forms?

I would guess that the following is very well known, but I don't know the answer and I couldn't find anything with some googling. Let $\Gamma \subset \mathrm{SL}(2,\mathbf Z)$ be a congruence ...
Dan Petersen's user avatar
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12 votes
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759 views

What numbers are integrally represented by $4 x^2 + 2 x y + 7 y^2 - z^3$

This is related to my first MO question and Kevin Buzzard's conjecture at Integers not represented by $ 2 x^2 + x y + 3 y^2 + z^3 - z $ In December 2010 my question appeared in the M.A.A. Monthly, ...
Will Jagy's user avatar
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12 votes
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Are there analogues of Beilinson's conjectures for motives with coefficients?

There's a body of wisdom (following Beilinson, Bloch, Deligne, ...) relating mixed Tate motives, motivic cohomology, algebraic K-theory, special values of L-functions, and polylogarithms. My ...
JBorger's user avatar
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11 votes
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359 views

What are the possible bad reductions for an abelian variety of dimension $g$ and a maximal endomorphism ring?

Perhaps the most basic fact about abelian varieties with CM is they have an everywhere potential good reduction (Serre-Tate). On the face of it it might appear that there isn't much more to be added ...
Vesselin Dimitrov's user avatar
11 votes
0 answers
324 views

Why is the CM-type preserved after base changing from char 0 to char p?

There is a transition in the theory of complex multiplication which seems to be glossed over in all expositions I can find. I would like to explicitly find a theorem that allows me to do this. ...
Catherine Ray's user avatar
8 votes
0 answers
420 views

Twists of CM modular forms

Let $K$ be an imaginary quadratic field of class number 1 and $E$ an elliptic curve over $\mathbf{Q}$ with CM by $\mathcal{O}_K$. Let $\psi$ be the Groessencharacter of $K$ attached to $E$, and $$ g_{...
David Loeffler's user avatar
7 votes
0 answers
482 views

Structure of elliptic curve $y^2 = x^3 - x$ over $\mathbb{F}_p$ with $p=(a+i)(a-i)$

I hope this question is good enough for this network. I am trying to compute the group structure as the title says of $E:y^2=x^3 - x$ over $\mathbb{F}_p$ with $p\equiv 1\bmod 8$ and $p-1$ a square, ...
Eduardo R. Duarte's user avatar
6 votes
0 answers
389 views

Kisin module for CM elliptic curve

Let $E$ be a CM elliptic curve with CM by the field $K$ and assume that $p$ is ramified in $K$ so that $\pi^2 = p \in \mathcal{O}_K$. In particular, then $E$ has supersingular reduction at $p$ and by ...
Vincent's user avatar
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5 votes
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241 views

$\mu=0$ for CM Elliptic curves?

Let $E$ be an elliptic curve defined over $F$ with CM by $\mathcal{O}_K$ where $K$ is an imaginary quadratic field. We may assume the $F$ contains $K$ and also contains the $p$-division points, where $...
debanjana's user avatar
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5 votes
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Principally Polarized CM Abelian Variety

I am interested in considering examples of abelian varieties that are principally polarized with CM in dimension three. However, I am struggling to construct or find even a single instance. In ...
KTT30's user avatar
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Real field of definition of an abelian variety of CM-type?

Question 0. Can a field of definitions (without automorphisms) of an (almost arbitrary) abelian variety of CM-type, originally defined over ${\mathbb{C}}$, be chosen to be a totally real number ...
Mikhail Borovoi's user avatar
4 votes
0 answers
249 views

Galois cohomology of the Serre group in the proof of the fundamental theorem of CM

I am working through J.S. Milne's note on the fundamental theorem of complex multiplication over $\mathbb{Q}$. Let $E$ be a CM-field Galois over $\mathbb{Q}$, and $S^E$ the Serre group corresponding ...
Jiangwei Xue's user avatar
4 votes
0 answers
139 views

About the main theorem of CM for elliptic curves

The classical main theorem of CM by Shimura states, among other things, that: Consider a quadratic imaginary $K/\mathbb Q$ and an elliptic curve $E= \mathbb C / \Lambda$ with CM s.t. $End(E)\otimes \...
BTF's user avatar
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Complex multiplication and ray class fields

This question is mainly referring to the proof of Theorem 5.6, Chapter 2 of Silverman's "Advanced Topics in the AEC". Basically, let $K$ be an imaginary quadratic field, and $E$ be an elliptic curve ...
ReHsu's user avatar
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359 views

Result of Deuring, intuitive way to see it's true/quickest way to prove?

There is the following result of Deuring that goes as follows: Let $E/L$ be an elliptic curve defined over a number field $L$ with complex multiplication by an order $\mathcal{O}$ in an imaginary ...
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4 votes
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modular curves with complex multiplication

Is the complete list of values of $N$ for which the modular curve $X_0(N)$ has complex multiplication? I guess the answer is no... Are there at least some examples known? The only one which comes ...
moodi's user avatar
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Formal non-CM in local fields

An elliptic curve $E$ with complex multiplication by an imaginary quadratic field $F$ has $\ell$-adic Galois representations that essentially encode the class field theory of $F$ - in other words, the ...
David Corwin's user avatar
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3 votes
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Are there CM complete intersections of arbitrarily large degree and codimension?

For every $d, c$ does there exist a smooth complete intersection $X \subset \mathbb{P}^N$ of codimension $c$ and multidegrees $d_1, \dots, d_c \ge d$ such that the Mumford-Tate group of $X$ is abelian?...
Ben C's user avatar
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3 votes
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Reference Request: CM Motives over Function Fields

Inspired by Schutt and Shioda's lovely "An interesting elliptic surface over an elliptic curve", I have been investigating the following surface: $$ \mathcal{E} : y^2 = x^3 - 27ux - 54v \...
Angus McAndrew's user avatar
3 votes
0 answers
199 views

Endomorphisms of elliptic curves, resp formal groups

Let $E$ be an elliptic curve over a number field $K$, $\mathcal{E}^w$ a fixed Weierstrass model for $E$ over $R := \mathbf{Z}[a_1,\ldots, a_6]$, $\mathcal{E}$ the Néron model of $\mathcal{E}$ over ...
user avatar
3 votes
0 answers
137 views

Values of Grössencharacter attached to CM elliptic curve

I am trying a cross-post here, as my previous post on stackexchange was not as fruitful as I hoped. The link to the older post is: https://math.stackexchange.com/questions/3327269/values-of-...
Jupp's user avatar
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3 votes
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95 views

CM abelian surfaces (computed locally)

Let $K$ be a CM field such that $[K:\mathbb{Q}] = 4$ and let $K^+\subseteq K$ be the totally real subfield of $K$. For simplicity, assume that $K/\mathbb{Q}$ is Galois and suppose that $p\in \mathbb{Z}...
Vincent's user avatar
  • 443
2 votes
0 answers
69 views

Question on a certain reduced isogeny of CM elliptic curves

My question has to do with some hypotheses showing up in a Lemma of Joseph Silverman's Advanced Topics book. Here is some of the set up: Let $K$ be an imaginary quadratic field and $E/H$ an elliptic ...
matt stokes's user avatar
2 votes
0 answers
255 views

Eisenstein Series at CM points

Suppose that $L= \mathbb{Z}\tau + \mathbb{Z}$ is a lattice with CM. Consider the Eisenstein sum $$ G_{2k}(L) = \sum_{(m,n)\neq (0,0)} \frac{1}{(m\tau+n)^{2k}}$$ where $k$ is a positive integer greater ...
Rdrr's user avatar
  • 881
2 votes
0 answers
135 views

Hasse invariant of abelian varieties with complex multiplication

Is there a good way to compute Hasse invariants of elliptic curves or higher dimensional Abelian varieties with complex multiplication? For example, if $E$ is an elliptic curve with CM by an ...
Jon Aycock's user avatar
2 votes
0 answers
229 views

field of definition of CM abelian varieties

When $A$ is a CM abelian variety of dimension $1$ (i.e., an elliptic curve), then we have a result that if it has CM by a maximal order then it has a model over a number field $F$ where $F$ is the ...
Vincent's user avatar
  • 443
2 votes
0 answers
377 views

Number of CM lifting of an ordinary elliptic curve

Before asking my questions I will start with an example: There are two CM elliptic curves over $\mathbb{Q}$ with CM field $\mathbb{Q}(\sqrt{-7})$, whose $j$-invariants are $-3^3.5^3$ and $3^3. 5^3. 17^...
user78039's user avatar
2 votes
0 answers
132 views

Genus 2 hyperelliptic cryptography : typical discriminant and class number

As far as I know, there is no standard yet for cryptography based on the DLP over Jacobians of genus 2 curves. Yet, what can we say about the class number, and the discriminant of the complex ...
Calodeon's user avatar
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2 votes
0 answers
161 views

CM Hodge structures

There are several definitions of Hodge structures with complex multiplication. One of them is the following: Definition. A Hodge structure $H$ is CM if it is polarizable and its Mumford-Tate group ...
cmhod's user avatar
  • 21
1 vote
0 answers
45 views

Abelian surface with CM by a prescribed quartic field

Given a quartic field $K$, is it possible to exhibit an explicit abelian surface $A$ defined over a number field with CM by the field $K$? For example, let's take the non-Galois CM-field $K=\mathbb Q(...
user413421's user avatar
1 vote
0 answers
96 views

When a CM abelian variety has complex multiplication by $\mathcal{O}_E$?

I'm reading Milne's note, Complex Multiplication. There are many properties, such as Shimura-Taniyama Formula provided that $A$ is an abelian variety with complex multiplication by $\mathcal{O}_E$. So ...
nzqr's user avatar
  • 59
1 vote
0 answers
91 views

Abelian group extensions

Let $K$ be an imaginary quadratic field and $E$ be an elliptic curve with CM by $\mathcal{O}_K$. Is there a way to see that $K(j(E), h(E[\mathfrak{p}]))/K$ is an Abelian extension for some $\mathfrak{...
debanjana's user avatar
  • 1,161
1 vote
0 answers
163 views

$F$-rational isogenies of CM Elliptic Curves

Let $F$ be a number field and $\mathcal{O}$ an order in an imaginary quadratic field $K$. Assume $K\subseteq F$. In Lang's Elliptic Functions, it is shown that over that there is a bijection between, ...
Rdrr's user avatar
  • 881
1 vote
0 answers
182 views

Can we choose $h(\mathcal{O})$ elliptic curves such that they have same trace and endomorphism ring $\mathcal{O}$ but distinct j-invariants?

Let $\mathbb{F}_q$ be a finite field of characteristic $p$ with $q=p^a$ elements. Let $E$ be an ordinary elliptic curve defined over $\mathbb{F}_q$. We know that $\text{End}(E)\otimes\mathbb{Q}$ is ...
tiansong's user avatar
  • 139
1 vote
0 answers
94 views

How quickly can we mutliply Cayley-Dickson hypercomplexes?

Assuming that all of the coordinates of two Cayley-Dickson Hypercomplex numbers are non-negative integers less than a prime $p$, how quickly can we multiply these numbers? I'm also interested in what ...
Matt Groff's user avatar
0 votes
0 answers
164 views

Why Lubin Tate character acts on torsion points of CM elliptic curve implies the group of torsion points is infinite?

Let $F$ be quadratic imaginary field, and $R_F$ be its ring of integers. Let $E /\Bbb{Q} $ be an elliptic curve which has CM by $F$. Suppose $E$ has good reduction at $P$,which is prime ideal of $R_F$....
Duality's user avatar
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0 votes
0 answers
120 views

field of definition of abelian varieties with extra endormorphism

Let $A$ be a complex abelian variety such that $\mathrm{End}(A)$ is strictly bigger than $\mathbb{Z}$. Question: Is is true that $A$ is defined over $\overline{\mathbb{Q}}$? This is of course what ...
vima's user avatar
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