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Seirios's user avatar
Seirios's user avatar
Seirios
  • Member for 11 years, 9 months
  • Last seen more than a month ago
64 votes
5 answers
6k views

If $e^A$ and $e^B$ commute, do $A$ and $B$ commute for finite dimensional matrices?

59 votes
3 answers
3k views

Explicit norm on $\mathcal{C}^0(\mathbb{R},\mathbb{R})$

29 votes
4 answers
16k views

Understanding proof of Cartan's magic formula: $L_X = i_X \circ d+d \circ i_X$

21 votes
3 answers
5k views

Line bundles of the circle

20 votes
1 answer
1k views

When is $\mathfrak{S}_n \times \mathfrak{S}_m$ a subgroup of $\mathfrak{S}_p$?

18 votes
1 answer
1k views

Cardinality of a locally compact Hausdorff space without isolated points

16 votes
1 answer
504 views

Gromov-Hausdorff convergence to a circle

14 votes
2 answers
4k views

Is the fundamental group of a compact manifold finitely presented?

14 votes
1 answer
757 views

Is there an injective $C^1$ curve dense in the plane?

14 votes
1 answer
4k views

Euler characteristic of a covering space

14 votes
1 answer
730 views

When is $G \ast H$ solvable?

13 votes
3 answers
1k views

Values taken by Euler's phi function

12 votes
2 answers
786 views

Which groups are derived subgroups?

12 votes
0 answers
163 views

Contracting subsets

11 votes
1 answer
465 views

Non-standard proofs of standard theorems

11 votes
1 answer
3k views

Is any Banach space a dual space?

11 votes
4 answers
1k views

Riemann hypothesis and diophantine equation

10 votes
1 answer
5k views

Lifting of maps to a covering space

10 votes
3 answers
662 views

Is $\langle a,b \mid a^2b^2=1 \rangle$ a semidirect product of $\mathbb{Z}^2$ and $\mathbb{Z}_2$?

10 votes
1 answer
768 views

Order topology and partial order

10 votes
1 answer
580 views

$D(G)$ is finite if $G$ has finitely many commutators

9 votes
3 answers
2k views

Some examples of virtually cyclic groups

9 votes
3 answers
335 views

Can divergent series be useful?

9 votes
1 answer
1k views

Not all finitely-presented groups are fundamental groups of closed 3-manifolds

8 votes
3 answers
249 views

Why does the sign $\times$ vanish in mathematical expressions?

8 votes
1 answer
319 views

(Un)distorted subgroups in $\mathbb{F}_2 \times \mathbb{F}_2$

8 votes
3 answers
2k views

Cayley complex as universal covering space

8 votes
2 answers
1k views

Is the injection $\ell^p \subset \ell^q$ continuous for $p<q$?

8 votes
2 answers
2k views

Every vector bundle over $[0,1]^n$ is trivial

7 votes
1 answer
489 views

How to draw by hand mathematical figures?