Hottest Questions This Month

47 votes

10 answers

5k views

What is the most "concrete-feeling" equivalent formulation of the Continuum Hypothesis that you can think of?

Jesse Elliott

4,113

modified Nov 28 at 8:07

52 votes

10 answers

6k views

A clear map of mathematical approaches to Artificial Intelligence

Akira

1,111

modified Dec 17 at 9:08

22 votes

2 answers

3k views

What is the minimal density of a set A such that A+A = N?

Jukka Kohonen

3,924

modified Dec 4 at 16:43

33 votes

4 answers

4k views

When has the scaffolding been more important than the completed building?

José Hdz. Stgo.

8,672

modified Nov 29 at 4:08

21 votes

5 answers

2k views

What phenomena are better modelled by SDE instead of ODE?

Rodrigo de Azevedo

2,256

answered Dec 19 at 18:07

22 votes

3 answers

2k views

What are some toy models for the stable homotopy groups of spheres?

Tim Campion♦

59k

modified Dec 3 at 2:34

10 votes

5 answers

2k views

Extracting a common convergent indexing from an uncountable family of sequences

Peter Mortensen

211

modified Dec 13 at 1:02

12 votes

1 answer

3k views

Is there a "halting machine" which halts on itself?

Joshua

103

modified Dec 15 at 18:10

23 votes

1 answer

1k views

Is every real number in [0,1] a product of three (or more) Cantor set's numbers?

John Bentin

2,427

modified 14 hours ago

11 votes

2 answers

2k views

Is GCH useful in proving theorems?

Mikhail Katz

14.9k

modified Nov 29 at 10:39

7 votes

1 answer

1k views

If two Lie algebras are isomorphic, under which conditions will their Lie groups also be isomorphic?

CommunityBot

1

modified Dec 10 at 20:05

2 votes

3 answers

383 views

Maximal set of $n$-bit strings that does not span $\mathbb{R}^n$

bof

10.8k

modified Dec 8 at 10:17

4 votes

2 answers

1k views

Does a function exist which is not Riemann integrable and satisfies the given condition:

bof

10.8k

modified Dec 13 at 7:29

20 votes

1 answer

871 views

Conjecture: Given any five points, we can always draw a pair of non-intersecting circles whose diameter endpoints are four of those points

Piquito

121

modified Dec 2 at 11:02

17 votes

1 answer

1k views

Explicit character tables of non-existent finite simple groups

Sebastien Palcoux

25.5k

modified Dec 19 at 4:58

5 votes

5 answers

871 views

Two arcs in the complement of a disc must intersect?

Wlod AA

4,674

modified Dec 4 at 21:27

14 votes

1 answer

939 views

Recognizing free groups

ThorbenK

1,055

modified Dec 4 at 7:15

3 votes

2 answers

540 views

Non-simple groups $G$ with only non-trivial quotient isomorphic to $G$

Dominic van der Zypen

44.5k

modified Nov 29 at 22:41

7 votes

2 answers

1k views

A curious martingale

Nate Eldredge

28.8k

modified Dec 17 at 16:45

15 votes

1 answer

1k views

Is this a typo in Macdonald's paper "The Poincaré Series of a Coxeter Group"?

Grant B.

806

answered Nov 30 at 16:23

8 votes

3 answers

636 views

Is "the purely probabilistic version of Freiling's axiom of symmetry" disprovable in ZFC?

Elliot Glazer

3,937

answered Dec 4 at 16:56

12 votes

2 answers

578 views

The mysterious significance of local subgroups in finite group theory

Geoff Robinson

41.8k

modified 11 hours ago

6 votes

1 answer

508 views

do all two manifolds admit a three-colorable triangulation?

David E Speyer

150k

answered 2 days ago

17 votes

1 answer

989 views

Is this an instance of the snake lemma?

John Rognes

8,547

modified yesterday

4 votes

2 answers

537 views

Computing hypergeometric function at 1

Hjalmar Rosengren

1,514

modified Dec 19 at 6:59

6 votes

4 answers

473 views

Countable chain condition in topology

Steven Clontz

933

answered Dec 8 at 14:34

5 votes

2 answers

391 views

On the number of distinct prime factors of $p^2+p+1$

CommunityBot

1

modified Dec 19 at 18:37

9 votes

2 answers

2k views

Is an easy proof of an interesting result worth publishing?

Dan Romik

2,430

answered Dec 16 at 9:02

2 votes

1 answer

682 views

Is $1 = \sum_{n=1}^{\infty} \frac{\pi(p_n^2)-n+2}{p_n^3-p_n}$ , where $\pi$ denotes the prime counting function and $p_n$ denotes the $n$-th prime?

CommunityBot

1

modified Dec 10 at 22:39

14 votes

1 answer

674 views

Euler's proof of $\frac{\pi}{6}=1-\frac{1}{2}-\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}-\cdots$

GH from MO

95.7k

modified Dec 3 at 19:48

32 votes

1 answer

1k views

Is there a regular pentagon with a rational point on each edge?

Peter Mueller

20.3k

modified Dec 8 at 6:54

5 votes

2 answers

374 views

When adding several $\sqrt[n]{p}$ to the rational numbers, what is the degree of field extension?

KConrad

49.1k

modified Dec 11 at 17:28

5 votes

3 answers

485 views

Congruences that aren't "finite from above"

Adam Přenosil

235

modified Dec 3 at 0:51

12 votes

1 answer

475 views

Generators for the first cohomology of free groups

Andy Putman

42.8k

answered Dec 18 at 22:21

9 votes

1 answer

537 views

Con(PA) via non-well-foundedness?

David Roberts♦

33.2k

modified Nov 30 at 23:22

6 votes

1 answer

507 views

In an abelian category with no nontrivial Serre subcategories, does every short exact sequence split?

Jeremy Rickard

33.2k

answered Dec 16 at 21:07

10 votes

1 answer

486 views

Can automorphism equivalence in a free group be detected in a nilpotent quotient?

Andy Putman

42.8k

modified Dec 19 at 21:16

3 votes

1 answer

552 views

binomial coefficients are integers because numerator and denominator form pairs?

GH from MO

95.7k

modified Dec 9 at 12:24

18 votes

2 answers

887 views

How to show a function converges to 1

Simd

3,095

modified Dec 13 at 8:45

8 votes

2 answers

483 views

On martingale convergence

Martin Hairer

8,684

modified 2 days ago

9 votes

1 answer

286 views

Where does the definition of ($\infty$-)groupoid cardinality come from?

LSpice

10.6k

modified yesterday

3 votes

3 answers

342 views

Closed formula for number of ones in a proper factor tree

Richard Stanley

48.7k

answered Dec 7 at 22:31

5 votes

2 answers

198 views

How much Dependent Choice is provable in $Z_2$? And what about Projective Determinacy?

Gabe Goldberg

7,074

modified 18 hours ago

9 votes

2 answers

486 views

Book for matroid polytopes

Tony Huynh

31.1k

modified Dec 12 at 20:58

6 votes

2 answers

601 views

Number of divisors which are at most $n$

GH from MO

95.7k

modified Dec 16 at 22:31

8 votes

2 answers

452 views

Faithful flatness and non-commutative algebras

LSpice

10.6k

modified Dec 5 at 21:18

10 votes

1 answer

566 views

Can a nowhere locally Hölder function be differentiable almost everywhere?

user479223

1,173

modified Dec 9 at 14:45

11 votes

2 answers

693 views

Generalisation of abelianisation using representation theory?

Geoff Robinson

41.8k

modified Dec 18 at 19:12

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