User Peter LeFanu Lumsdaine - Mathematics Stack Exchange

10 votes

Can the limit of a product exist if neither of its factors exist?

answered Oct 3, 2013 at 22:43

9 votes

Must a sequence be well-founded?

answered Sep 19, 2018 at 13:28

9 votes

does the uniform continuity of $f$ implies uniform continuity of $f^2$ on $\mathbb{R}$?

answered Jul 20, 2012 at 22:02

8 votes

Accepted

A set is open if its complement is closed.

answered Oct 16, 2012 at 5:43

8 votes

Accepted

Why doesn't the definition of (model-theoretic) conservative extension need strengthening?

answered Sep 2, 2013 at 16:46

8 votes

How do algebraists intuitively picture normal subgroups and ideals?

answered Dec 1, 2016 at 16:16

8 votes

Why should we care about syntactic proofs if we can show semantically that statements are true?

answered Aug 10, 2019 at 21:28

7 votes

What is the difference between "expectation", "variance" for statistics versus probability textbooks?

answered Dec 24, 2020 at 1:50

7 votes

Accepted

The (standard) definition of a group.

answered Oct 15, 2020 at 9:07

7 votes

Why haven't I heard of the Hausdorff quotient?

answered Feb 17, 2023 at 17:31

7 votes

Accepted

When is it possible to interpret composition as a natural transformation?

answered Jan 28, 2015 at 14:44

7 votes

Question about the category $\textbf{2}$

answered Jan 8, 2014 at 12:11

6 votes

Non-associative commutative binary operation

answered Jan 23, 2016 at 22:19

6 votes

Accepted

Products in a subcategory

answered Dec 1, 2012 at 23:37

6 votes

Ratio test and the Root test

answered Apr 7, 2012 at 23:18

6 votes

Elevator pitch for a (sub)field of maths?

answered Oct 15, 2010 at 15:25

6 votes

Accepted

Multisets don't have addition

answered Sep 3, 2023 at 21:05

5 votes

Is this a good enough proof by induction?

answered Apr 16, 2020 at 20:49

5 votes

What's the background of this exercise?

answered Nov 29, 2012 at 6:12

5 votes

Proving Dedekind finite implies finite assuming countable choice

answered Dec 3, 2012 at 18:00

4 votes

A category's quotient category of isomorphism types

answered Sep 3, 2013 at 15:26

4 votes

Accepted

How to find recurrence relation for this problem?

answered Dec 1, 2012 at 23:23

4 votes

Accepted

Covering space of a wedge of two circles

answered Feb 21, 2011 at 6:46

4 votes

Accepted

What does $0^-$ mean in set or type theory?

answered May 15, 2016 at 3:10

4 votes

Number of solutions for a given logical equation

answered Sep 10, 2018 at 10:00

4 votes

Accepted

How to find the number of intersections of diagonals in icosahedron?

answered Jan 7, 2014 at 11:54

4 votes

What is the difference between a Hamel basis and a Schauder basis?

answered Jan 7, 2014 at 16:57

4 votes

What does "maximum value" of a set of random variables mean?

answered Jan 19, 2018 at 14:08

4 votes

Accepted

If you equip two isomorphic groups with homeomorphic topologies, are they isomorphic as topological groups?

answered Mar 17, 2020 at 8:52

4 votes

Differences between groups and rings when understood as categories

answered May 11, 2022 at 10:48

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116 Answers

Can the limit of a product exist if neither of its factors exist?

Must a sequence be well-founded?

does the uniform continuity of $f$ implies uniform continuity of $f^2$ on $\mathbb{R}$?

A set is open if its complement is closed.

Why doesn't the definition of (model-theoretic) conservative extension need strengthening?

How do algebraists intuitively picture normal subgroups and ideals?

Why should we care about syntactic proofs if we can show semantically that statements are true?

What is the difference between "expectation", "variance" for statistics versus probability textbooks?

The (standard) definition of a group.

Why haven't I heard of the Hausdorff quotient?

When is it possible to interpret composition as a natural transformation?

Question about the category $\textbf{2}$

Non-associative commutative binary operation

Products in a subcategory

Ratio test and the Root test

Elevator pitch for a (sub)field of maths?

Multisets don't have addition

Is this a good enough proof by induction?

What's the background of this exercise?

Proving Dedekind finite implies finite assuming countable choice

A category's quotient category of isomorphism types

How to find recurrence relation for this problem?

Covering space of a wedge of two circles

What does $0^-$ mean in set or type theory?

Number of solutions for a given logical equation

How to find the number of intersections of diagonals in icosahedron?

What is the difference between a Hamel basis and a Schauder basis?

What does "maximum value" of a set of random variables mean?

If you equip two isomorphic groups with homeomorphic topologies, are they isomorphic as topological groups?

Differences between groups and rings when understood as categories