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4 votes
0 answers
8k views

Which proportion of elliptic curves over Q is proved to satisfy BSD conjecture?

In 2014, Bhargava and other authors proved that more than 66 % of all elliptic curves defined over $ \mathbb{Q} $ satisfy the Birch and Swinnerton-Dyer conjecture. Tonight I stumbled upon an article …
Sylvain JULIEN's user avatar
2 votes
0 answers
5k views

A system of linear equations with linear constraints

Mathematical problem. Suppose we have $2n$ indeterminates $x_1,\dots,x_n$ and $y_1,\dots,y_n$ (which are denoted by $q$ with indices and called abundances below) and $m$ subsets $P_1,\dots,P_m$ of $\l …
Florian Breitwieser's user avatar
4 votes
0 answers
5k views

E[ | X - Y | ] where X and Y are independent Poisson random variable

What is the expected value of the absolute difference of two independent Poisson variables? $$E[ |X - Y| ]$$ Seems like an easy question but I haven't found an easy solution. I've split the double …
mathsguy1's user avatar
46 votes
0 answers
6k views

Cochains on Eilenberg-MacLane Spaces

Let $p$ be a prime number, let $k$ be a commutative ring in which $p=0$, and let $X = K( {\mathbb Z}/p {\mathbb Z}, n)$ be an Eilenberg-MacLane space. Let $F$ be the free $E_{\infty}$-algebra over $k$ …
Jacob Lurie's user avatar
  • 17.8k
6 votes
0 answers
8k views

Dual space of continuous functions

Let $C_b(\Omega,V )=$ { $ f:\Omega\rightarrow V $ } is the Banach space of all bounded continuous functions in Banach space $V$ with a norm $\|\cdot\|$ defined as $\|f\|_\infty=\sup _{x\in\Omega}\|f(x …
Mariarty's user avatar
  • 385
23 votes
0 answers
8k views

An $n \times n$ matrix $A$ is similar to its transpose $A^{\top}$: elementary proof?

A famous result in linear algebra is the following. An $n \times n$ matrix $A$ over a field $\mathbb{F}$ is similar to its transpose $A^T$. I know one proof using the Smith Normal Form (SNF). Ho …
Sungjin Kim's user avatar
  • 3,320
8 votes
0 answers
6k views

Convex hulls of compact sets

Let $A$ be a compact set in a separable Hilbert space $H$, and let $\bar A$ denote its convex hull. Is $\bar A$ compact?
Tom LaGatta's user avatar
  • 8,512
10 votes
0 answers
6k views

Atiyah's paper "Non-existent complex 6-sphere"

I'm trying to understand the main idea of Atiyah's proof (https://arxiv.org/abs/1610.09366). Although there were discussions on MO year ago I couldn't find answers to my questions. Consider the isomo …
Max Borovkov's user avatar
50 votes
0 answers
12k views

Atiyah's paper on complex structures on $S^6$

M. Atiyah has posted a preprint on arXiv on the non-existence of complex structure on the sphere $S^6$. https://arxiv.org/abs/1610.09366 It relies on the topological $K$-theory $KR$ and in particula …
David C's user avatar
  • 9,870
8 votes
0 answers
8k views

Intersection of open affines is affine

I would like to see a clear, rigorous and elementary proof of the following statement: Let X be a (not necessary quasi-projective, separated) algebraic variety over the complex numbers, and let U,V b …
Qfwfq's user avatar
  • 23.4k
12 votes
0 answers
13k views

A New York Times tiles-based graph theory question

The New York Times has a daily puzzle named Tiles that works as follows. Start with $m$ squares (in the official version, this is 30, in a 6x5 grid), and a set of $p>4$ possible patterns (typically th …
David Pepper's user avatar
48 votes
0 answers
17k views

What is the current understanding regarding complex structures on the 6-sphere?

In October 2016, Atiyah famously posted a preprint to the arXiv, "The Non-Existent Complex 6-Sphere" containing a very brief proof $S^6$ admits no complex structure, which I immediately read and reali …
jdc's user avatar
  • 2,995
16 votes
0 answers
11k views

Deligne's letter to Jean-Pierre Serre

I'm looking for another letter of Pierre Deligne, this time to Jean-Pierre Serre (from around 1974 I think), in which he proves that the Galois representation associated to a certain Hecke eigenform i …
Przemyslaw Chojecki's user avatar
2 votes
0 answers
6k views

Automorphisms of the L-function associated to an elliptic $\mathbb{Q}$-curve

$\DeclareMathOperator\Aut{Aut}\newcommand{\alg}{\mathrm{alg}}\newcommand{\an}{\mathrm{an}}$Edited after Noam Elkies' comment: From what I understand (very little actually), there exist elliptic curves …
Sylvain JULIEN's user avatar
24 votes
0 answers
13k views

Philosophy behind Zhang's 2022 preprint on the Landau–Siegel zero

Now that a week has passed since Zhang posted his preprint Discrete mean estimates and the Landau–Siegel zero on the arXiv, I'm wondering if someone can give a high-level overview of his strategy. In …
Stopple's user avatar
  • 11.1k

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