User kjo

449 votes

22 answers

29k views

On "familiarity" (or How to avoid "going down the Math Rabbit Hole"?)

asked Dec 24, 2013 at 22:08

293 votes

41 answers

22k views

Can't argue with success? Looking for "bad math" that "gets away with it"

asked Dec 17, 2012 at 11:51

74 votes

4 answers

4k views

Laplace, Legendre, Fourier, Hankel, Mellin, Hilbert, Borel, Z...: unified treatment of transforms?

asked Jun 8, 2013 at 13:47

58 votes

4 answers

12k views

How to interpret the adjoint?

asked Jun 22, 2013 at 20:22

41 votes

1 answer

22k views

What's the difference between material implication and logical implication?

asked Oct 1, 2011 at 2:34

38 votes

3 answers

9k views

Why isn't the orbit-stabilizer theorem obvious?

asked Jan 14, 2014 at 3:26

35 votes

4 answers

5k views

Looking for student's guide to diagram chasing

asked Jul 30, 2011 at 11:30

29 votes

11 answers

9k views

Looking for a clear definition of the geometric product

asked Jul 16, 2013 at 12:43

25 votes

2 answers

5k views

When is a pullback also a pushout?

asked Nov 12, 2011 at 12:58

23 votes

3 answers

2k views

On the importance of natural transformations

asked Jul 14, 2015 at 15:31

19 votes

3 answers

912 views

How to recognize adjointness?

asked Apr 6, 2014 at 20:41

18 votes

4 answers

3k views

Why the words "inner" and "outer" to designate products?

asked Jun 21, 2013 at 13:41

18 votes

5 answers

574 views

Looking for Cover's hubris-busting ${\mathbb R}^{N\gg3}$ counterexamples

asked Jan 29, 2013 at 2:29

16 votes

5 answers

2k views

Algebraic topology, etc. for Mac Lane's "Categories for the Working Mathematician"

asked Dec 2, 2011 at 12:51

15 votes

5 answers

6k views

What is the categorical diagram for the tensor product?

asked Jan 20, 2012 at 0:48

15 votes

1 answer

362 views

Is there a smooth strictly-increasing bijection $\mathbb{R} \to (0, 1)$ that maps $\mathbb{Q}$ onto $\mathbb{Q}\cap(0, 1)$?

asked May 24, 2022 at 20:41

14 votes

3 answers

2k views

What is the insight behind the Lebesgue integral?

asked Jan 24, 2012 at 4:55

14 votes

3 answers

371 views

Is the thingie/cothingie distinction absolute?

asked Feb 25, 2012 at 21:49

14 votes

3 answers

1k views

Natural uses for the co-product of sets?

asked Mar 3, 2014 at 12:54

13 votes

2 answers

1k views

What's the dual of "inverse image" in Set?

asked Nov 8, 2011 at 19:56

13 votes

3 answers

1k views

What's wrong with this definition of continuity?

asked Jan 4, 2012 at 12:21

12 votes

2 answers

1k views

Need construction for coequalizer in $\mathbf{Poset}$

asked Feb 26, 2012 at 20:04

11 votes

3 answers

509 views

Finding a more direct way to reach $\mathbb{E} \left( \sum (X_i - \mu)^2 \right) - \mathbb{E} \left( \sum (X_i - \overline{X})^2 \right) = \sigma^2$

asked Apr 5, 2013 at 11:03

11 votes

1 answer

636 views

Mystified by Rotman's proof of normality of index-2 subgroups

asked Dec 8, 2011 at 12:57

11 votes

3 answers

4k views

Conditions for "monic $\iff$ injective"?

asked Jul 23, 2011 at 23:44

11 votes

3 answers

1k views

What are integrating factors, really?

asked Apr 5, 2014 at 15:20

10 votes

1 answer

1k views

Looking for a a measure-theoretic treatment of "differential entropy"

asked Apr 10, 2014 at 23:26

9 votes

1 answer

222 views

Is there any advantage to the $a \equiv b\;\;(\mathrm{mod}\;c)$ notation?

asked Mar 16, 2014 at 17:19

9 votes

2 answers

2k views

On the identity map requirement in the definition of category

asked Oct 4, 2015 at 21:33

9 votes

1 answer

878 views

On "small triangles" in a square lattice

asked May 30, 2017 at 0:34

Stack Exchange Network

198 Questions

On "familiarity" (or How to avoid "going down the Math Rabbit Hole"?)

Can't argue with success? Looking for "bad math" that "gets away with it"

Laplace, Legendre, Fourier, Hankel, Mellin, Hilbert, Borel, Z...: unified treatment of transforms?

How to interpret the adjoint?

What's the difference between material implication and logical implication?

Why isn't the orbit-stabilizer theorem obvious?

Looking for student's guide to diagram chasing

Looking for a clear definition of the geometric product

When is a pullback also a pushout?

On the importance of natural transformations

How to recognize adjointness?

Why the words "inner" and "outer" to designate products?

Looking for Cover's hubris-busting ${\mathbb R}^{N\gg3}$ counterexamples

Algebraic topology, etc. for Mac Lane's "Categories for the Working Mathematician"

What is the categorical diagram for the tensor product?

Is there a smooth strictly-increasing bijection $\mathbb{R} \to (0, 1)$ that maps $\mathbb{Q}$ onto $\mathbb{Q}\cap(0, 1)$?

What is the insight behind the Lebesgue integral?

Is the thingie/cothingie distinction absolute?

Natural uses for the co-product of sets?

What's the dual of "inverse image" in Set?

What's wrong with this definition of continuity?

Need construction for coequalizer in $\mathbf{Poset}$

Finding a more direct way to reach $\mathbb{E} \left( \sum (X_i - \mu)^2 \right) - \mathbb{E} \left( \sum (X_i - \overline{X})^2 \right) = \sigma^2$

Mystified by Rotman's proof of normality of index-2 subgroups

Conditions for "monic $\iff$ injective"?

What are integrating factors, really?

Looking for a a measure-theoretic treatment of "differential entropy"

Is there any advantage to the $a \equiv b\;\;(\mathrm{mod}\;c)$ notation?

On the identity map requirement in the definition of category

On "small triangles" in a square lattice