22
votes

Accepted

### Can I ask a question on MathOverflow and also on another site?

Cross-posting is discouraged in general, because it can lead to duplication of effort by people answering on different sites. However, it is appropriate under some circumstances.
Most of the advice ...

Tim CampionMod

- 56.7k

19
votes

### Best of MathOverflow, or papers inspired by MathOverflow

My MO question Conjugation of group extensions was answered by YCor. As a result, we wrote a joint note
Conjugate complex homogeneous spaces with non-isomorphic fundamental groups published in C. R. ...

Community wiki

15
votes

### Best of MathOverflow, or papers inspired by MathOverflow

As acknowledged in my note Explicit additive decomposition of norms on $\mathbb{R}^2$, it was sparked by answers by Noam D. Elkies and Suvrit Sra on MathOverflow Absolute value inequality for complex ...

Community wiki

13
votes

### Best of MathOverflow, or papers inspired by MathOverflow

A nice question by Michael Hardy, How many rearrangements must fail to alter the value of a sum before you conclude that none do?, led to a recent 6-author collaboration, 5 or 6 of whom are MO patrons ...

Community wiki

12
votes

### Best of MathOverflow, or papers inspired by MathOverflow

This MO question was the starting point for a joint work with Tao Mei where we study radial multipliers on the von Neumann algebras of hyperbolic groups. The paper is entitled Complete boundedness of ...

Community wiki

12
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Keith Kearnes, together with co-authors Emil Kiss and Ágnes Szendrei, recently published a solution to Varieties where every algebra is free in this arxiv preprint. They prove a result under an even ...

Community wiki

11
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Not sure if my recent paper "Equivalence: an attempt at a history of the idea" qualifies as one of the "best of Mathoverflow or papers inspired by Mathoverflow". But I am sure Mathoverflow was a force ...

Community wiki

11
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Hannah Cairns's proof of Perron's theorem (discussed in this MathOverflow question) has been published in The American Mathematical Monthly as Perron’s Theorem in an Hour.

Community wiki

10
votes

### Best of MathOverflow, or papers inspired by MathOverflow

An unpublished open problem posed by Adam Chalcraft, Does every polyomino tile $\mathbb R^n$ for some $n$?, received considerable attention when I posted it here on MO. (Of all the questions that I ...

Community wiki

10
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Mohammad Ghomi answered
the question
Shortest closed curve to inspect a sphere,
in a paper, Shortest closed curve to inspect a sphere, posted to the arXiv (https://arxiv.org/abs/2010.15204),
whose PDF ...

Community wiki

10
votes

### Best of MathOverflow, or papers inspired by MathOverflow

This paper,
Roman Karasev, Jan Kynčl, Pavel Paták, Zuzana Safernová, and Martin Tancer. "Bounds for Pach's selection theorem and for the minimum solid angle in a simplex." arXiv:1403.8147 (2014).
...

Community wiki

10
votes

### Best of MathOverflow, or papers inspired by MathOverflow

The MO question, "Shortest closed curve to inspect a sphere,"
was cited as the "initial stimulus" for the paper
Mohammad Ghomi, "The length, width,and inradius of space curves,"
(PDF download.)
...

Community wiki

9
votes

### Best of MathOverflow, or papers inspired by MathOverflow

In 2013 John Pardon solved the Hilbert-Smith conjecture for group actions on 3-manifolds.
Lemma 2.17 of the paper was based on the answer to this mathoverflow question. I was quite surprised to ...

Community wiki

9
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Julien Marché's question "Homology generated by lifts of simple curves" was the first appearance in print of a folklore question (I first was asked it back when I was a postdoc). As I discuss in my ...

Community wiki

8
votes

### Best of MathOverflow, or papers inspired by MathOverflow

The full answer to the question Decidability of diophantine equation in a theory by rainmaker in the case of Robinson’s arithmetic was written up in my paper Division by zero, Archive for Mathematical ...

Community wiki

8
votes

### Best of MathOverflow, or papers inspired by MathOverflow

This doesn't quite fit the mold of the other postings, but Matt Parker
(Numberphile
and StandUpMaths)
made
a YouTube video
that mentions MathOverflow
several times, and particularly highlights the ...

Community wiki

7
votes

### Best of MathOverflow, or papers inspired by MathOverflow

My Forum of Mathematics Sigma paper (published 2021) answered a 20-year old question of Jeff Shallit. The proof makes crucial use of ideas in a 2016 MO answer by Anthony Quas.

Community wiki

7
votes

### Best of MathOverflow, or papers inspired by MathOverflow

This paper of mine (Arithmetic Restrictions on Geometric Monodromy) was inspired in large part by this question asked by Lisa S., though the original motivation is not so obvious in the final product.

Community wiki

7
votes

### Best of MathOverflow, or papers inspired by MathOverflow

The paper "Majority colourings of digraphs" by Paul Seymour, Stephan Kreutzer, Sang-il Oum, David R. Wood and myself has its origin in my question "Majority coloring for directed graphs".

Community wiki

7
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Joachim König has answered my question
Order of products of elements in symmetric groups
in his paper A note on the product of two permutations of prescribed orders,
to appear in European Journal of ...

Community wiki

6
votes

### Best of MathOverflow, or papers inspired by MathOverflow

The paper, "A quantitative obstruction to collapsing surfaces," by Mikahil G. Katz,
arXiv abs, addresses the MO question, "Gromov-Hausdorff limits of 2-dimensional Riemannian surfaces" posed by sva (S....

Community wiki

6
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Quoting Oscar Cunningham's answer to an MO question asking for decision problems that are not known to be decidable:
In Conway's Game of Life, the problem of deciding whether a given pattern with ...

Community wiki

5
votes

### Best of MathOverflow, or papers inspired by MathOverflow

This paper addresses and partially solves a question posed by Matthew Kahle,
whose MO question they explicitly cite:
chromatic number of the hyperbolic plane.
DeCorte, Evan, and Konstantin Golubev....

Community wiki

5
votes

### Best of MathOverflow, or papers inspired by MathOverflow

The discussion initiated by my question
Primes occurring as orders of elements of a finitely presented group
led to the addition of Section 5 to:
Maurice Chiodo, On torsion in finitely presented ...

Community wiki

5
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Leonardo Zapponi has answered my question
Parametric solutions of Pell's equation
in his paper Parametric solutions of Pell equations.

Community wiki

5
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Garabed Gulbenkian's 2010 question about ordinal definable real numbers, which Joel David Hamkins called "a fascinating, outstanding question," attracted considerable attention, culminating ...

Community wiki

5
votes

### Best of MathOverflow, or papers inspired by MathOverflow

I just learned that a question of mine on minimal vertex covers in hypergraphs where edges intersect in at most $1$ point led to a paper by Lajos Soukup and Tamas Csernak; it will appear in Discrete ...

Community wiki

4
votes

### Best of MathOverflow, or papers inspired by MathOverflow

This MO question "Property $\Gamma$ in terms of correspondences" led us to answer two old open problems and to push further a third more recent result:
Jon Bannon, Amine Marrakchi, Narutaka Ozawa. ...

Community wiki

4
votes

### Best of MathOverflow, or papers inspired by MathOverflow

Zhi-Wei Sun posted a highly upvoted MO question in 2018, Can we write each positive rational number as ${1\over p_1−1}+\cdots+{1\over p_k−1}$ with $p_1,\ldots,p_k$ distinct primes? The question ...

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