Questions tagged [arithmetic-geometry]
Diophantine equations, rational points, abelian varieties, Arakelov theory, Iwasawa theory.
2,220 questions
10
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Why did we miss a cohomology theory of “Weil type”?
It’s a well known fact due to Serre that there is no $\mathbf Q_p$- and $\mathbf R$-valued cohomology theory of “Weil type” for varieties over $\overline{\mathbf F_p}$; but for $\ell\ne p$, a $\mathbf ...
2
votes
0
answers
169
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Deformation of abelian scheme
Let $A/k$ be an abelian variety over a characteristic $p>0$ perfect field $k$. Usually, we say $A$ admits a lift to $W_2(k)$ if there exists an abelian scheme $\mathcal{A}/W_2(k)$ such that $\...
2
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0
answers
106
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Reference request: Integral motivic cohomology of $BG$
Are there references that compute the integral motivic cohomology $\mathrm{H}^{p,q}(BG,\mathbb Z)$, for $G$ finite cyclic and where $BG$ is defined over the rationals.
I am particularly interested in $...
0
votes
0
answers
50
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Linear-Disjointness of the field obtained upon iterated pre-images
Suppose $K$ is a number field and we have finitely many elements $\alpha_{1}, \ldots, \alpha_{k} \in K$ and a polynomial $f(x)\in K[x]$ of degree $\geq 2$. Given $m \geq 1$, we define $K_{m}(\alpha_{i}...
2
votes
0
answers
183
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Irreducibility of a degree-$27$ polynomial through Newton polygon or residual reduction
Let $K=\mathbb{Q}_3(t)$ be the finite extension of the $3$-adic number field $\mathbb{Q}_3$, where $t=3^{1/13}$. I want to know if the polynomial $$f(x)=(x^9-t^2)^3-3^4x+3^3t^5 \in K[x]$$ is ...
2
votes
1
answer
370
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Reduction of an abelian variety
Let $T_1, T_2, ..., T_g$ be the local co-ordinates of Tangent space of an Abelian variety of dimension $g$ around the identity $O$. Let $P \in A(K)$ and $v$ be a non-archimedean place of number field $...
4
votes
1
answer
199
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Frobenius action on component group of Néron model
Let $p$ be an odd prime. Suppose an elliptic curve $E/\mathbb{Q}$ has reduction of type $I_n$ at $p$. Let $\mathcal{E}$ be its Néron model, and assume that the component group $\tilde{\mathcal{E}}/\...
2
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0
answers
156
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Does analytic rank always upper bound algebraic rank over function fields?
Let $A$ be an abelian variety over a global function field. Is the Mordell-Weil rank of $A$ known to be at most the analytic rank, i. e. the order at $s = 1$ of the $L$-function? This is stated in ...
1
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0
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64
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Rational points on Abelian variety with infinitely many zero reduction
Let $J$ be an abelian variety over a number field $K$, and $x \in J(K)$ be a $K$-ratinal point of $J$. Suppose that for infinitely many non-archimedean valuation $v$ of $K$, (where $J$ has good ...
1
vote
1
answer
137
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Transition maps $\mathcal S_{K_p'K^p} \to \mathcal S_{K_pK^p}$ between integral models of Shimura varieties at two different parahoric levels
Given a Shimura datum $(G,X)$ of abelian type, for $K_p \subset G(\mathbb Q_p)$ a parahoric subgroup and $K^p \subset G(\mathbb A_f^p)$ an open compact subgroup which is small enough, there is an ...
2
votes
0
answers
78
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Independence of rational points of abelian varieties after localization
Let $K$ be a number field, $X$ a smooth projective curve over $K$ with genus $g$. Let $J$ be the jacobian of $X$ with $j: X \to J$, let $r$ be the rank of the $\mathbb Z$-module $J(K)$.
We may choose ...
6
votes
1
answer
300
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Etale cohomological dimension of affinoid perfectoid spaces for $\ell$-torsion sheaves ($\ell \ne p$)
Let $X$ be an affinoid perfectoid space of characteristic either $0$ or $p$. It is well known that for a $p$-torsion sheaf $\mathcal F$, $H^i(X_{et}, \mathcal F)=0$ for $i>1$ (see Scholze's comment ...
5
votes
1
answer
377
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Relationship between Shimura varieties and the moduli stack of principal bundles on a curve
I'm aware of two "geometric" constructions of automorphic forms. The first is in terms of Shimura varieties. A Shimura variety is (roughly speaking) a moduli space of abelian varieties with ...
11
votes
2
answers
749
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Result seemingly quoted from SGA
I'm looking for the following result in SGA quoted in Grothendieck's "Groupes de Barsotti-Tate et Cristaux de Dieudonne" via a translation of Peterson:
Let $S$ be a scheme over $\mathbb{F}_p$...
3
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0
answers
407
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Are discrete topological modules (light) solid?
Recall two definitons:
Let $\mathrm P_{\mathbb Z} = \mathbb Z[\overline{\mathbb N}] / \mathbb Z[\infty]$ denote the free condensed abelian group on null sequences.
A condensed abelian group $M$ is ...
5
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0
answers
225
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Locally Separated Morphism of Sheaves
Definition 9.2.2 of Scholze and Weinstein's Berkeley Lectures on $p$-adic Geometry says "Consider the site Perf of perfectoid spaces of characteristic $p$ with the pro-ètale topology. A map $f:\...
3
votes
0
answers
125
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Kernel of $\operatorname{Br}(F) \to \prod_v \operatorname{Br}(F_v)$ and the Tate–Shafarevich group
Let $X$ be a smooth projective curve over a number field $K$ which has a $K$-rational point, and let $F = K(X)$ be its function field. Consider the map
$$
\operatorname{Br}(F) \longrightarrow \prod_v \...
0
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0
answers
135
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Tate/semisimplicity conjecture for resolution of nodal quartic surface
Thanks to work of many people (Madapusi, Charles, Maulik...) the Tate conjecture is now known for K3 surfaces over any finitely generated field. A smooth quartic surface is K3. Consider instead a ...
4
votes
1
answer
194
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Are abelian varieties over $\mathbb{F}_q[t]$ which have the same $L$-function isogenous?
Faltings' isogeny theorem implies that two abelian varieties over a number field $K$ which have the same characteristic polynomial of Frobenius at almost all primes are isogenous. If $K = \mathbb{Q}$ ...
2
votes
0
answers
147
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Find a ring R such that Spec R is homeomorphic to Spa(Z,Z)
I'm following Scholze-Weinstein's Berkeley notes (https://www.math.uni-bonn.de/people/scholze/Berkeley.pdf). And there is a theorem by Huber (Thm 2.3.3) in the notes that says the adic spectrum $\...
8
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0
answers
245
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Is the solvable closure of $\mathbb{F}_p(t)$ PAC?
It is a famous open problem in field arithmetic whether $\mathbb{Q}^{\mathrm{solv}}$, the solvable closure of $\mathbb{Q}$, is pseudo algebraically closed (PAC). That is, whether every absolutely ...
2
votes
0
answers
246
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Why is the notion of $(\phi,\Gamma)$-module useful?
I have a, hopefully not so stupid, feeling that the notion of $(\phi,\Gamma)$-modules is an abstract model for $p$-adic Galois representations.
I am wondering what is good for us when we work with ...
2
votes
0
answers
100
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Quasi-isogeny corresponding to the image of the Frobenius in the Dieudonné module of a $p$-divisible group
Let $X$ be a $p$-divisible group over a perfect field $k$ of characteristic $p>0$. Let $M(X)$ be the covariant Dieudonné module of $X$. Thus, $M(X)$ is a finite free $W(k)$-module equipped with a $\...
3
votes
0
answers
262
views
Need copy of old preprint: "Arithmetic of Fermat varieties I, Fermat motives and p-adic cohomologies" by Suwa-Yui
Illusie's article in volume II of the Grothendieck Festschrift cites a 1988 preprint: "Arithmetic of Fermat varieties I, Fermat motives
and p-adic cohomologies", by Suwa-Yui. It does not ...
3
votes
1
answer
307
views
Chebotarev density for function fields
In On $l$-independence of Algebraic Monodromy Groups in Compatible Systems of Representations, they stated such an example (Example 6.3):
Let $X$ be a connected normal scheme of finite type over $\...
3
votes
0
answers
173
views
The quadratic forms corresponding to canonical (Neron-Tate) height of an elliptic curve
Surely this is well-known in the arithmetic geometry community, which I (unfortunately) do not regard as a member of, so I will include some basic exposition for the laymen (including myself).
We deal ...
2
votes
0
answers
195
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Explicit description of the crystal associated to the universal object on a Lubin-Tate space
Let $X:=\mathrm{LT}_h$ be the Lubin-Tate space of the (unique) formal group law of height $h$ over $k:=\overline{\mathbb{F}}_p$. The adic generic fiber $X_{\eta}=\mathrm{LT}_{h,\eta}$ is then a rigid-...
0
votes
0
answers
117
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Confusion on theorem in paper on monodromy of $p$-rank strata of moduli of curves
Application 5.7 in "Monodromy of the $p$-rank strata of the moduli space of curves", by Achter and Pries,
seems to imply that for $g \ge 3$, there exists a supersingular smooth projective ...
1
vote
0
answers
265
views
Vanishing of Weil–Châtelet group over solvably closed field
Let $A$ be a connected algebraic group defined over a solvably closed field $K$. Are there any results concerning the vanishing of the WC-group $H^1(G_K, A)$?
4
votes
1
answer
236
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If two non-isomorphic cubic surfaces over a field $k$ have all their lines defined over $k$, can they become isomorphic over the algebraic closure?
If two non-isomorphic smooth cubic surfaces over a field $k$ each contain 27 lines defined over $k$, can they become isomorphic over the algebraic closure?
4
votes
0
answers
261
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$L$-function form of Tate conjecture for divisors on abelian varieties
Let $k$ be the function field of a $d$-dimensional regular integral finite-type scheme $Y$ over $\mathbb{Z}$. Conjecture 2 in Tate's paper in the Woods Hole proceedings predicts (among other things) ...
1
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0
answers
246
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Does $\text{Gal}(K(F[\pi^{\infty}])/K \cong \text{Gal}(K(G[\pi^{\infty}])/K$ imply $F[\pi^n] \cong G[\pi^n]$?
Let $K$ be a $p$-adic number field with ring of integers $\mathcal{O}_K$ and uniformizer $\pi$. Let $F$ and $G$ be two $d$-dimensional formal groups of height $h$ over $\mathcal{O}_K$. Denote:
\begin{...
4
votes
1
answer
464
views
Semisimplicity of crystalline Frobenius
Let $X$ denote a smooth proper scheme over a finite field $k$ of characteristic $p$. It is my understanding that it is not generally known if the Frobenius action on the rationalized crystalline ...
1
vote
0
answers
67
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Horizontal sections of the unit‑root sub‑isocrystal for GM-connection, and equivalence with local systems
Let $Y\to X$ denote a relative abelian scheme, with $X$ smooth proper over $k$ a finite field of characteristic $p$. Let $\mathcal{V} := R^1_{\mathrm{cr}}f_*\textbf{1}[1/p]$ denote the Gauss-Manin $F$-...
1
vote
0
answers
217
views
Nilpotence of De Rham cohomology in positive characteristic
I am trying to show that if $\pi: X\rightarrow S, f: S\rightarrow T$ are smooth morphisms over positive characteristic. Then $(\mathbb{H}^i_{dR}(X/S), \nabla_{GM})$ is nilpotent, in the sense of Katz (...
7
votes
1
answer
330
views
How big can the degree of the field of definition of a morphism of abelian variety be?
Excuse me if some parts of the questions are well known, I am still a PhD student and have a lot to learn.
This question came to me while doing research on the Coleman's conjecture (as presented in a ...
2
votes
1
answer
338
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Canonical descent of Serre-Tate canonical lift
Deligne seems to say on page 239 here that the Serre-Tate canonical lift of an ordinary abelian variety over the algebraic closure $\overline{k}$ of a finite field of characteristic $p$ canonically ...
7
votes
1
answer
245
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what is space moduli space of higher-dimensional formal group law?
Let $k$ be a perfect field and $W(k)$ be the ring of Witt vector and define the ring of formal power series $$R:=W(k)[[v_1, \cdots, v_{h-1}]]$$ in $h-1$ variables. Then there is a canonical surjection ...
2
votes
0
answers
194
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What is the Dirichlet density of the reducible locus in the moduli of polarized abelian varieties in positive characteristic?
By section 2 of https://swc-math.github.io/aws/2024/2024KaremakerNotes.pdf, for $q = p^r$ a prime power, any $g, d \ge 1$, and any $n \ge 3$ prime to $q$, there exists a stratified fine moduli space $...
5
votes
1
answer
229
views
$\mathbb{Z}_p^{\mathbb{N}}$-extension and formal Drinfeld module
Thanks for your help. I'm reading the paper Iwasawa main conjecture for the Carlitz cyclotomic extension and applications (https://arxiv.org/pdf/1412.5957). I find three questions about the motivation ...
5
votes
1
answer
460
views
When does the Kodaira symbol determine the Tamagawa number?
Let $E/K$ be an elliptic curve over a local field. I understand that the Kodaira type of $E/K$ refers to the isomorphism class of the special fiber of the Néron minimal model of $E/K$ as a scheme over ...
1
vote
0
answers
188
views
Rational points of abelian varieties over finite fields
Let $A$ be an abelian variety over a finite field $k$ and $\ell$ a prime number. Fix a natural number $n\in \mathbb{N}$ and denote by $k_{n}$ the field $k(A[\ell^{n}](\overline k))$. Let $Q\in A[\ell^{...
5
votes
2
answers
508
views
Do Frobenius elements at closed points topologically generate the fundamental group?
For $X$ a regular (or perhaps just normal) variety over Spec $\mathbb{Z}$, is the etale fundamental group of $X$ topologically generated by Frobenius elements at closed points? This is true when $X$ ...
2
votes
0
answers
262
views
Why is the category of Weil-étale sheaves abelian with enough injectives?
When I study Weil-étale cohomology put forward by S. Lichtenbaum in the paper The Weil-étale topology on schemes over finite fields, I find two questions.
Let $X$ be a scheme of finite type over a ...
2
votes
0
answers
162
views
Deligne local constant
Let $F$ be a non-Archimedean local field. For a multiplicative character $\chi$ of $F^\times$, let $a(\chi)$ be the conductor of $\chi$. For a nontrivial additive character $\phi$ of $F$, we denote ...
1
vote
0
answers
98
views
Line bundle and height on abelian variety
Let $A$ be an abelian variety over a number field $K$ of dimension $g$. Consider $\mathcal{L}$ be a symmetric ample line on $A$ that gives an embedding $ \ i_{\mathcal{L}} : A(\overline{K}) \...
2
votes
0
answers
198
views
How could we get the Weil group for global function fields?
Thanks for your help. I know the definition of Weil group and how to get it for $p$-adic local field cases. By reading the answer https://math.stackexchange.com/a/2898449/1007843, I write down my ...
2
votes
0
answers
132
views
Section of abelian variety over local field
Let $K$ be a non-archimedean local field (e.g., $\mathbb{Q}_p$ ), $A / K$ an abelian variety of dimension $g$. Consider $\mathcal{L}$ a line bundle on $A$ and $F \in \Gamma(A, \mathcal{L})$ a global ...
3
votes
0
answers
228
views
Neron model of dual abelian variety
Let $A/K$ be an abelian variety where $K = \operatorname{Frac}(R)$ for some discrete valuation ring $R$. Let $\mathcal{A}$ be its Neron model. Assume that $A$ has potential good reduction, so that the ...
2
votes
0
answers
158
views
Infinitude of points on a rank 1 elliptic curve satisfying a "geometric" condition
A friend recently nerd-sniped me with a (seemingly elementary) geometry question:
Let $\triangle ABC$ (with corresponding side lengths $a$, $b$, and $c$) be an obtuse triangle with $\angle C > 90^\...