User Ville Salo

21 votes

4 answers

2k views

Units in the group ring over fours group after Gardam

asked Mar 6, 2021 at 10:42

16 votes

3 answers

2k views

If the center of a finite group is trivial, are there two elements whose centralizers intersect trivially?

gr.group-theory

asked Apr 24, 2018 at 9:27

13 votes

1 answer

586 views

Splendid groups

gr.group-theory topological-groups

asked Aug 27, 2020 at 12:26

12 votes

0 answers

269 views

Does the Angel have to be really smart?

computational-complexity combinatorial-game-theory

asked Jun 2, 2020 at 1:48

12 votes

0 answers

475 views

Is homeomorphism of simplicial complexes semidecidable?

gn.general-topology computability-theory

asked Sep 13, 2018 at 9:19

12 votes

1 answer

420 views

Can matrices over $F[G]$ have infinite order when $G$ is periodic?

gr.group-theory

asked Sep 2, 2019 at 13:42

10 votes

1 answer

581 views

How can you order a free group?

gr.group-theory order-theory free-groups ordered-groups

asked Jan 21, 2020 at 14:10

7 votes

4 answers

567 views

Roots in Thompson's groups

gr.group-theory

asked Feb 16, 2021 at 8:17

6 votes

1 answer

258 views

Which groups contain a comb?

gr.group-theory graph-theory geometric-group-theory

asked Mar 19, 2019 at 19:06

6 votes

1 answer

176 views

Is there a prefix-continuous bijection between finite words and eventually zero words?

co.combinatorics geometric-group-theory combinatorics-on-words

asked May 28, 2020 at 8:16

6 votes

0 answers

130 views

Difficulty of homeomorphism of effective Cantor dynamics

ds.dynamical-systems computability-theory symbolic-dynamics

asked Sep 7, 2020 at 15:03

6 votes

1 answer

252 views

Examples of "natural" finitely generated groups with an undecidable conjugacy problem

gr.group-theory computability-theory

asked Sep 21, 2020 at 12:41

6 votes

2 answers

402 views

Which groups are doubling?

gr.group-theory mg.metric-geometry geometric-group-theory

asked Oct 28, 2020 at 13:16

4 votes

2 answers

268 views

Reversible polynomial circuit = polynomial reversible circuit?

gr.group-theory finite-groups computational-complexity permutations

asked Jan 21, 2019 at 12:26

4 votes

0 answers

149 views

Distortion in the Brin-Thompson 2V

gr.group-theory geometric-group-theory

asked May 12 at 6:54

4 votes

1 answer

157 views

Topologically mixing cellular automata on groups

gr.group-theory ds.dynamical-systems cellular-automata

asked Jun 30, 2020 at 9:34

4 votes

0 answers

191 views

Finitely-generated amenable group isomorphic to its square

gr.group-theory

asked Jan 8, 2021 at 6:52

3 votes

1 answer

186 views

Finitely-generated conjugation action on a subgroup that is not normal... what is that?

reference-request gr.group-theory notation

asked Feb 22, 2021 at 8:52

3 votes

1 answer

185 views

Convex sets on the discrete Heisenberg group

gr.group-theory convex-geometry

asked Dec 15, 2019 at 8:44

3 votes

1 answer

159 views

Monotile that tiles when you apply a rubber band

mg.metric-geometry discrete-geometry tiling physics

asked Jun 13, 2020 at 22:04

2 votes

0 answers

179 views

$V$-like actions of $V$

co.combinatorics gr.group-theory geometric-group-theory combinatorics-on-words

asked May 29, 2020 at 9:19

2 votes

0 answers

58 views

Are there finitely-presented astral monoids?

semigroups-and-monoids

asked Oct 4, 2019 at 13:46

2 votes

1 answer

104 views

A detail about busy beaverly behavior of distortion functions in graph groups

gr.group-theory computability-theory

asked Aug 26, 2020 at 10:08

1 vote

2 answers

273 views

Impredictable subsets of $\mathbb{N}$

computability-theory

asked Mar 9, 2020 at 13:20

1 vote

1 answer

47 views

If the union of finitely many conjugacy classes is syndetic, are there finitely many conjugacy classes?

gr.group-theory

asked Nov 30, 2020 at 12:43

1 vote

0 answers

39 views

If the union of finitely many conjugacy classes hits large enough difference sets, are ther finitely many conjugacy classes?

gr.group-theory

asked Nov 30, 2020 at 14:15

0 votes

0 answers

80 views

QI-closure of $\mathrm{NA}\times\mathrm{NA}$

gr.group-theory geometric-group-theory

asked May 19, 2020 at 19:07

0 votes

0 answers

42 views

Is there a reversible fully polynomial-time approximation scheme for polygonal billiards?

discrete-geometry computational-complexity billiards

asked Jul 6, 2020 at 17:11

Stack Exchange Network

current community

your communities

more stack exchange communities

28 Questions

Units in the group ring over fours group after Gardam

If the center of a finite group is trivial, are there two elements whose centralizers intersect trivially?

Splendid groups

Does the Angel have to be really smart?

Is homeomorphism of simplicial complexes semidecidable?

Can matrices over $F[G]$ have infinite order when $G$ is periodic?

How can you order a free group?

Roots in Thompson's groups

Which groups contain a comb?

Is there a prefix-continuous bijection between finite words and eventually zero words?

Difficulty of homeomorphism of effective Cantor dynamics

Examples of "natural" finitely generated groups with an undecidable conjugacy problem

Which groups are doubling?

Reversible polynomial circuit = polynomial reversible circuit?

Distortion in the Brin-Thompson 2V

Topologically mixing cellular automata on groups

Finitely-generated amenable group isomorphic to its square

Finitely-generated conjugation action on a subgroup that is not normal... what is that?

Convex sets on the discrete Heisenberg group

Monotile that tiles when you apply a rubber band

$V$-like actions of $V$

Are there finitely-presented astral monoids?

A detail about busy beaverly behavior of distortion functions in graph groups

Impredictable subsets of $\mathbb{N}$

If the union of finitely many conjugacy classes is syndetic, are there finitely many conjugacy classes?

If the union of finitely many conjugacy classes hits large enough difference sets, are ther finitely many conjugacy classes?

QI-closure of $\mathrm{NA}\times\mathrm{NA}$

Is there a reversible fully polynomial-time approximation scheme for polygonal billiards?