User Lee Mosher

54 votes

When has discrete understanding preceded continuous?

answered May 29, 2017 at 13:47

45 votes

Accepted

Conjugacy classes of $\mathrm{SL}_2(\mathbb{Z})$

answered Apr 13, 2016 at 22:31

40 votes

Accepted

Connected sum of topological manifolds

answered Feb 12, 2013 at 19:17

37 votes

Is rigour just a ritual that most mathematicians wish to get rid of if they could?

answered Apr 25, 2013 at 18:17

34 votes

Why are free objects "free"?

answered Oct 29, 2017 at 15:56

29 votes

Kirby's torus trick

answered Mar 2, 2017 at 3:15

28 votes

Occurrences of (co)homology in other disciplines and/or nature

answered May 20, 2012 at 14:10

24 votes

Do mathematicians rely on senses other than vision and hearing?

answered Mar 28, 2023 at 15:53

22 votes

Instances where an existence result precedes the constructive version

answered Aug 15, 2012 at 1:34

21 votes

Group theory with grep?

answered Apr 14, 2022 at 13:15

20 votes

Actions on Sⁿ with quotient Sⁿ

answered Jul 25, 2012 at 13:19

20 votes

Accepted

Periodic automorphisms of free groups

answered Apr 25, 2012 at 21:25

19 votes

Fundamental groups of noncompact surfaces

answered Mar 30, 2012 at 22:53

19 votes

How can a mathematician handle the pressure to discover something new?

answered Mar 11, 2018 at 15:25

18 votes

Subgroups of $SL_2(\mathbb R)$ which contain $SL_2(\mathbb Z)$ as a finite index subgroup

answered Oct 12, 2016 at 23:47

17 votes

Accepted

$\operatorname{Out}(F_n)$ is not linear for $n > 3$

answered May 17, 2018 at 20:43

17 votes

Are there some other notions of "curvature" which measure how space curves?

answered Dec 1, 2013 at 16:59

15 votes

Accepted

Universal covering of compact surfaces

answered May 25, 2013 at 18:57

15 votes

Was the early calculus inconsistent?

answered Mar 20, 2013 at 14:45

14 votes

Why is the fundamental group of a compact Riemann surface not free ?

answered Apr 7, 2012 at 2:00

14 votes

Is each closed convex set a manifold with corners?

answered Sep 28, 2015 at 15:21

13 votes

Accepted

Integer matrix that does not belong to a free group of rank 2

answered Nov 10, 2015 at 20:35

13 votes

When can a class in $H^1(M;\mathbb{Z})$ be represented by a fiber bundle over $S^1$

answered May 17, 2015 at 23:28

13 votes

Finite subgroups of mapping class groups

answered Aug 31, 2014 at 15:46

13 votes

Why are Fuchsian groups interesting?

answered Jan 23, 2017 at 14:59

13 votes

Continuous notions with compelling discrete analogues

answered Aug 19, 2012 at 16:00

13 votes

Demystifying complex numbers

answered Mar 22, 2013 at 16:43

13 votes

Compelling evidence that two basepoints are better than one

answered Apr 21, 2013 at 14:31

13 votes

Accepted

Kernel of linear representation of Baumslag-Solitar group

answered Nov 14, 2012 at 1:30

13 votes

Accepted

The role of the Automatic Groups in the history of Geometric Group Theory

answered May 13, 2013 at 16:08

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218 Answers

When has discrete understanding preceded continuous?

Conjugacy classes of $\mathrm{SL}_2(\mathbb{Z})$

Connected sum of topological manifolds

Is rigour just a ritual that most mathematicians wish to get rid of if they could?

Why are free objects "free"?

Kirby's torus trick

Occurrences of (co)homology in other disciplines and/or nature

Do mathematicians rely on senses other than vision and hearing?

Instances where an existence result precedes the constructive version

Group theory with grep?

Actions on Sⁿ with quotient Sⁿ

Periodic automorphisms of free groups

Fundamental groups of noncompact surfaces

How can a mathematician handle the pressure to discover something new?

Subgroups of $SL_2(\mathbb R)$ which contain $SL_2(\mathbb Z)$ as a finite index subgroup

$\operatorname{Out}(F_n)$ is not linear for $n > 3$

Are there some other notions of "curvature" which measure how space curves?

Universal covering of compact surfaces

Was the early calculus inconsistent?

Why is the fundamental group of a compact Riemann surface not free ?

Is each closed convex set a manifold with corners?

Integer matrix that does not belong to a free group of rank 2

When can a class in $H^1(M;\mathbb{Z})$ be represented by a fiber bundle over $S^1$

Finite subgroups of mapping class groups

Why are Fuchsian groups interesting?

Continuous notions with compelling discrete analogues

Demystifying complex numbers

Compelling evidence that two basepoints are better than one

Kernel of linear representation of Baumslag-Solitar group

The role of the Automatic Groups in the history of Geometric Group Theory