User Dominic van der Zypen

10 votes

2 answers

244 views

Minimal refinements of open covers of $T_2$-spaces

asked Apr 24, 2018 at 14:33

10 votes

1 answer

477 views

Is $\mathbb{R}^\omega \cong (\mathbb{R}^\omega \setminus \{x\})$?

asked Jun 7, 2018 at 15:46

10 votes

0 answers

254 views

Fixed point property for simple undirected graphs

asked Oct 27, 2017 at 9:39

10 votes

1 answer

291 views

Curious decomposition between two sets

asked Aug 14, 2017 at 6:54

10 votes

2 answers

473 views

Are all monomorphisms in the category of bounded lattices regular?

asked Apr 15, 2015 at 5:56

10 votes

3 answers

675 views

Collection of dense subsets as a "fingerprint" for Hausdorff topologies?

asked Feb 8, 2016 at 8:47

10 votes

1 answer

3k views

Travelling Salesman Problem: Can the nearest neighbor algorithm be $n$ times longer than the optimal solution?

asked Jun 26, 2015 at 6:35

10 votes

4 answers

588 views

Graph homomorphisms and line graph

asked Oct 1, 2015 at 9:11

9 votes

1 answer

372 views

Generalized geometries

asked Jul 15, 2015 at 7:55

9 votes

3 answers

830 views

Majority coloring for directed graphs

asked Mar 7, 2016 at 15:27

9 votes

2 answers

503 views

Graph $G$ with $\omega(G) = 2$ but $\chi(G) \geq \aleph_0$

asked May 20, 2015 at 9:34

9 votes

2 answers

2k views

"Gray code" of all permutations

asked Aug 29, 2017 at 12:34

9 votes

3 answers

407 views

Does the lattice of all topologies embed into the lattice of $T_1$-topologies?

asked Mar 13, 2018 at 9:41

9 votes

1 answer

513 views

Does "$X \not\to (\omega)^\omega_2$ for every infinite $X$" imply ${\sf AC}$?

asked Mar 21, 2022 at 10:28

9 votes

1 answer

247 views

Non-Ramsey functions $c:[\omega]^\omega\to\{0,1\}$ and the Axiom of Choice

asked Jul 18, 2023 at 16:08

9 votes

1 answer

387 views

Example of a connected graph $G$ with $G \cong G \times G$

asked Aug 4, 2022 at 7:15

9 votes

1 answer

364 views

Are the Boolean algebras ${\cal P}(\omega)/(\text{fin})$ and ${\cal P}(\omega)/(\text{thin})$ isomorphic?

asked Dec 21, 2023 at 15:33

9 votes

3 answers

493 views

Countable connected space where removing $1$ point destroys connectedness

asked Dec 25, 2018 at 8:35

9 votes

2 answers

437 views

Lower density of numbers not summable by consecutive integers

asked Oct 14, 2018 at 13:35

9 votes

0 answers

326 views

Uncountable group with no proper subgroup of maximal cardinal

asked Oct 30, 2019 at 16:39

9 votes

1 answer

460 views

Min–max reversing bijections $f:\mathbb{N}\to\mathbb{N}$

asked Jun 12 at 20:01

8 votes

1 answer

257 views

Maximal Ramsey families

asked Nov 12 at 15:34

8 votes

3 answers

583 views

Arranging all permutations on $\{1,\ldots,n\}$ such that there are no common points

asked May 29, 2019 at 11:29

8 votes

1 answer

598 views

Expected value of biggest distance of adjacent points uniformly picked in $[0,1]$

asked Jul 3, 2019 at 7:39

8 votes

2 answers

707 views

Exponential objects in the category of measurable spaces

asked Jul 13, 2019 at 19:44

8 votes

1 answer

261 views

Set of homeomorphic fixed points that is dense, but not equal to whole space

asked Sep 3, 2018 at 12:56

8 votes

4 answers

714 views

Are there $2^{\aleph_0}$ pairwise non-isomorphic Boolean algebra structures on $\omega$?

asked Feb 23, 2019 at 16:09

8 votes

2 answers

509 views

Bijection $\varphi:\mathbb{N}\to\mathbb{N}$ that distorts every finite arithmetic progression

asked Jun 4 at 10:25

8 votes

1 answer

721 views

How "correct" is Knuth's fast addition $(a,b) \mapsto (a \oplus b) \oplus ((a\land b) \ll 1)$?

asked Sep 19, 2023 at 20:40

8 votes

1 answer

478 views

Scheduling "parent talks" at school

asked Jan 8, 2023 at 19:53

Stack Exchange Network

1,209 Questions

Minimal refinements of open covers of $T_2$-spaces

Is $\mathbb{R}^\omega \cong (\mathbb{R}^\omega \setminus \{x\})$?

Fixed point property for simple undirected graphs

Curious decomposition between two sets

Are all monomorphisms in the category of bounded lattices regular?

Collection of dense subsets as a "fingerprint" for Hausdorff topologies?

Travelling Salesman Problem: Can the nearest neighbor algorithm be $n$ times longer than the optimal solution?

Graph homomorphisms and line graph

Generalized geometries

Majority coloring for directed graphs

Graph $G$ with $\omega(G) = 2$ but $\chi(G) \geq \aleph_0$

"Gray code" of all permutations

Does the lattice of all topologies embed into the lattice of $T_1$-topologies?

Does "$X \not\to (\omega)^\omega_2$ for every infinite $X$" imply ${\sf AC}$?

Non-Ramsey functions $c:[\omega]^\omega\to\{0,1\}$ and the Axiom of Choice

Example of a connected graph $G$ with $G \cong G \times G$

Are the Boolean algebras ${\cal P}(\omega)/(\text{fin})$ and ${\cal P}(\omega)/(\text{thin})$ isomorphic?

Countable connected space where removing $1$ point destroys connectedness

Lower density of numbers not summable by consecutive integers

Uncountable group with no proper subgroup of maximal cardinal

Min–max reversing bijections $f:\mathbb{N}\to\mathbb{N}$

Maximal Ramsey families

Arranging all permutations on $\{1,\ldots,n\}$ such that there are no common points

Expected value of biggest distance of adjacent points uniformly picked in $[0,1]$

Exponential objects in the category of measurable spaces

Set of homeomorphic fixed points that is dense, but not equal to whole space

Are there $2^{\aleph_0}$ pairwise non-isomorphic Boolean algebra structures on $\omega$?

Bijection $\varphi:\mathbb{N}\to\mathbb{N}$ that distorts every finite arithmetic progression

How "correct" is Knuth's fast addition $(a,b) \mapsto (a \oplus b) \oplus ((a\land b) \ll 1)$?

Scheduling "parent talks" at school