User Bjørn Kjos-Hanssen

58 votes

Is there a measure zero set which isn't meagre?

answered Oct 25, 2010 at 5:20

43 votes

Suggestions for good notation

answered Oct 20, 2010 at 21:02

37 votes

Accepted

Examples of mathematical papers that contain a kind of research report

answered Nov 21, 2018 at 7:46

36 votes

Accepted

If all balls at $x$ and $y$ are isometric is there an isometry sending $x$ to $y$?

answered Oct 6, 2014 at 17:15

33 votes

Accepted

Is there a known Turing machine which halts if and only if the Collatz conjecture has a counterexample?

answered Sep 15, 2018 at 10:47

32 votes

Accepted

On sentences true in all finite groups

answered May 24, 2015 at 3:45

25 votes

Accepted

What is the reverse mathematical strength of the fundamental theorem of algebra?

answered Jun 30, 2015 at 1:35

25 votes

Accepted

Languages beyond enumerable

answered Apr 21, 2016 at 1:40

21 votes

Accepted

History of powers beyond squares and cubes

answered Sep 19, 2014 at 1:45

21 votes

Why is the Gaussian so pervasive in mathematics?

answered Sep 28, 2010 at 9:01

21 votes

Accepted

Question arising from Voevodsky's talk on inconsistency

answered Oct 5, 2010 at 22:51

21 votes

For which Millennium Problems does undecidable -> true?

answered Apr 11, 2014 at 16:37

20 votes

Accepted

Are countable dense subspaces of $\mathbb{R}^n$ homeomorphic to ${\mathbb Q}^n$?

answered Sep 14, 2017 at 6:11

20 votes

Accepted

Why is weak Kőnig's lemma weaker than Kőnig's lemma?

answered Nov 1, 2019 at 21:44

19 votes

Accepted

Is Turing degree actually useful in real life?

answered Feb 14, 2014 at 19:17

18 votes

Why is this new result such a big deal?

answered May 27, 2016 at 0:04

18 votes

In what sense is GCD an extension of boolean OR?

answered Dec 6, 2016 at 7:15

17 votes

Intuition of law of iterated logarithm?

answered Apr 20, 2014 at 8:11

17 votes

Probably true, but provably unprovable

answered Nov 16, 2018 at 21:43

15 votes

Accepted

Is min exponents of three positive integers $n$, $n+1$ and $n+2$ $=1$ true or false?

answered Sep 22, 2019 at 6:57

15 votes

Calculate in closed form $\int_0^1 \int_0^1 \frac{dx\,dy}{1-xy(1-x)(1-y)}$

answered May 18, 2015 at 21:37

14 votes

A set for which it is hard to determine whether or not it is countable.

answered Mar 22, 2011 at 2:14

13 votes

Accepted

Example of a function that behaves like another function

answered Sep 27, 2010 at 9:15

13 votes

Interesting meta-meta-mathematical theorems?

answered Mar 8, 2014 at 16:31

13 votes

Accepted

Can any finite lattice be realized as an intermediate subgroups lattice?

answered Feb 8, 2015 at 21:17

13 votes

Examples of $\aleph_0$-categorical nonhomogeneous structures

answered Jul 15, 2020 at 19:19

13 votes

How did the Baker-Gill-Solovay paper come to be?

answered Aug 20, 2020 at 7:02

13 votes

Why would one number theorems, propositions and lemmas separately?

answered Aug 2, 2019 at 22:33

12 votes

Accepted

Is the collection of primitive recursive functions a lower set in the poset of computable functions?

answered Jun 30, 2020 at 7:29

12 votes

Why do we need random variables?

answered Sep 23, 2016 at 6:30

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415 Answers

Is there a measure zero set which isn't meagre?

Suggestions for good notation

Examples of mathematical papers that contain a kind of research report

If all balls at $x$ and $y$ are isometric is there an isometry sending $x$ to $y$?

Is there a known Turing machine which halts if and only if the Collatz conjecture has a counterexample?

On sentences true in all finite groups

What is the reverse mathematical strength of the fundamental theorem of algebra?

Languages beyond enumerable

History of powers beyond squares and cubes

Why is the Gaussian so pervasive in mathematics?

Question arising from Voevodsky's talk on inconsistency

For which Millennium Problems does undecidable -> true?

Are countable dense subspaces of $\mathbb{R}^n$ homeomorphic to ${\mathbb Q}^n$?

Why is weak Kőnig's lemma weaker than Kőnig's lemma?

Is Turing degree actually useful in real life?

Why is this new result such a big deal?

In what sense is GCD an extension of boolean OR?

Intuition of law of iterated logarithm?

Probably true, but provably unprovable

Is min exponents of three positive integers $n$, $n+1$ and $n+2$ $=1$ true or false?

Calculate in closed form $\int_0^1 \int_0^1 \frac{dx\,dy}{1-xy(1-x)(1-y)}$

A set for which it is hard to determine whether or not it is countable.

Example of a function that behaves like another function

Interesting meta-meta-mathematical theorems?

Can any finite lattice be realized as an intermediate subgroups lattice?

Examples of $\aleph_0$-categorical nonhomogeneous structures

How did the Baker-Gill-Solovay paper come to be?

Why would one number theorems, propositions and lemmas separately?

Is the collection of primitive recursive functions a lower set in the poset of computable functions?

Why do we need random variables?