User Peter LeFanu Lumsdaine - Mathematics Stack Exchange

288 votes

Accepted

How do you explain to a 5th grader why division by zero is meaningless?

answered Aug 15, 2018 at 11:42

42 votes

Accepted

An interesting problem with "decomposing" natural numbers.

answered Oct 29, 2020 at 22:48

26 votes

Given an infinite number of monkeys and an infinite amount of time, would one of them write Hamlet?

answered Jan 13, 2011 at 5:37

24 votes

Accepted

A polynomial is completely determined by any part of it

answered Dec 14, 2019 at 23:31

21 votes

Accepted

In category theory why is a right adjoint not a left adjoint?

answered Nov 22, 2011 at 4:34

21 votes

Accepted

Which step in this process allows me to erroneously conclude that $i = 1$

answered Nov 22, 2011 at 4:10

20 votes

Direct sums and direct products

answered Dec 1, 2012 at 17:02

19 votes

Accepted

Is every monoid isomorphic to its opposite

answered Sep 4, 2013 at 16:40

17 votes

Is this of any real importance to the mathematical scientific community?

answered Dec 30, 2013 at 18:47

17 votes

How would you explain to a 9th grader the negative exponent rule?

answered Jan 7, 2014 at 14:41

17 votes

Where is the mistake in the argument in favor of the (erroneous) claim "every Dedekind cut is a rational cut"?

answered May 11 at 7:06

16 votes

Accepted

Prove that $x^4-y^4=1996$ has no integer root.

answered Jul 8, 2016 at 8:57

16 votes

A Question about Doctoral Theses in Mathematics

answered May 22, 2013 at 4:23

15 votes

$\sqrt 2$ is even?

answered Jun 6, 2013 at 16:52

13 votes

Finite covering is compact Hausdorff iff base space is

answered Dec 16, 2012 at 7:28

13 votes

Given that it appears impossible to make the set out of linear combinations of its elements, why is it still dependent?

answered Mar 15, 2015 at 3:32

13 votes

Can somebody explain to me Cantor's diagonalization argument?

answered Oct 7, 2013 at 0:03

13 votes

Understanding Universal Quantifiers (Order Matters)

answered Feb 21, 2023 at 12:44

12 votes

Accepted

Why not $\{\{a\},\{b, \emptyset \}\}$ as the ordered pairs?

answered Jan 25, 2023 at 17:24

12 votes

In homotopy type theory, what are the intermediate values along a path?

answered Jul 18, 2022 at 8:03

12 votes

Why is two to the power of zero equal to binary one?

answered Oct 15, 2010 at 5:52

11 votes

Why $\mathbb{R}[X]/(X^2+1)\cong\mathbb{C}$?

answered Jun 7, 2013 at 14:56

11 votes

Why is the Principle of Explosion considered constructive?

answered Jun 29, 2023 at 13:57

11 votes

Does a homeomorphism preserve the open sets?

answered Apr 12 at 20:21

11 votes

In how many ways the letters of the word "LOCKDOWN" can be arranged such that N is always between O's?

answered Jul 11, 2023 at 16:12

10 votes

Accepted

Is "William only eats icecream when the sun is shining" a biimplication?

answered Sep 12, 2023 at 7:20

10 votes

Definition of presheaf, given in Basic Algebraic geometry 2 Shafarevich

answered Jan 15, 2023 at 17:59

10 votes

Examples of non-continuous, non-piecewise-constant, idempotent map?

answered May 20, 2020 at 14:26

10 votes

What's so special with small categories?

answered Nov 20, 2010 at 2:51

10 votes

Partitioning an infinite set

answered Dec 1, 2010 at 15:54

Stack Exchange Network

116 Answers

How do you explain to a 5th grader why division by zero is meaningless?

An interesting problem with "decomposing" natural numbers.

Given an infinite number of monkeys and an infinite amount of time, would one of them write Hamlet?

A polynomial is completely determined by any part of it

In category theory why is a right adjoint not a left adjoint?

Which step in this process allows me to erroneously conclude that $i = 1$

Direct sums and direct products

Is every monoid isomorphic to its opposite

Is this of any real importance to the mathematical scientific community?

How would you explain to a 9th grader the negative exponent rule?

Where is the mistake in the argument in favor of the (erroneous) claim "every Dedekind cut is a rational cut"?

Prove that $x^4-y^4=1996$ has no integer root.

A Question about Doctoral Theses in Mathematics

$\sqrt 2$ is even?

Finite covering is compact Hausdorff iff base space is

Given that it appears impossible to make the set out of linear combinations of its elements, why is it still dependent?

Can somebody explain to me Cantor's diagonalization argument?

Understanding Universal Quantifiers (Order Matters)

Why not $\{\{a\},\{b, \emptyset \}\}$ as the ordered pairs?

In homotopy type theory, what are the intermediate values along a path?

Why is two to the power of zero equal to binary one?

Why $\mathbb{R}[X]/(X^2+1)\cong\mathbb{C}$?

Why is the Principle of Explosion considered constructive?

Does a homeomorphism preserve the open sets?

In how many ways the letters of the word "LOCKDOWN" can be arranged such that N is always between O's?

Is "William only eats icecream when the sun is shining" a biimplication?

Definition of presheaf, given in Basic Algebraic geometry 2 Shafarevich

Examples of non-continuous, non-piecewise-constant, idempotent map?

What's so special with small categories?

Partitioning an infinite set