User Noah Schweber

40 votes

7 answers

11k views

What are some proofs of Godel's Theorem which are essentially different from the original proof?

asked Aug 4, 2011 at 3:35

38 votes

19 answers

5k views

Counterexamples in universal algebra

asked Jan 9, 2014 at 2:51

34 votes

2 answers

2k views

Ur-elemental surprises

asked Dec 21, 2022 at 2:24

32 votes

1 answer

2k views

Godel on recursion-theoretic hierarchies

asked Mar 26, 2013 at 4:52

28 votes

0 answers

2k views

Supercompact and Reinhardt cardinals without choice

asked Apr 23, 2012 at 1:53

27 votes

0 answers

1k views

Where do uncountable models collapse to?

asked Oct 14, 2015 at 4:45

26 votes

2 answers

2k views

On the global structure of the Gromov-Hausdorff metric space

asked Jul 26, 2015 at 17:42

25 votes

2 answers

1k views

Detecting uncountable cardinals in $(\mathbb{R};+,\times,\mathbb{N})$

asked Jul 27, 2021 at 0:05

25 votes

6 answers

2k views

Are there infinitely many "generalized triangle vertices"?

asked Nov 7, 2021 at 22:38

24 votes

9 answers

2k views

Self-containing structures

asked Mar 24, 2013 at 2:03

22 votes

1 answer

725 views

Undetermined Banach-Mazur games in ZF?

asked Jan 31, 2020 at 21:26

21 votes

2 answers

1k views

Gently changing measure

asked Jan 9, 2020 at 16:47

21 votes

2 answers

1k views

Antirandom reals

asked Sep 27, 2015 at 1:28

21 votes

1 answer

827 views

Relative null-ness

asked Sep 21, 2015 at 4:03

20 votes

3 answers

2k views

A limit to Shoenfield Absoluteness

asked Aug 3, 2011 at 5:25

20 votes

1 answer

1k views

Is "almost-solvability" of Diophantine equations decidable?

asked Aug 2, 2021 at 0:34

20 votes

1 answer

1k views

Does sine interact equationally with addition alone?

asked Jun 14, 2021 at 16:50

19 votes

1 answer

874 views

Topological universal algebra: what is a variety?

asked May 28, 2017 at 20:48

19 votes

0 answers

791 views

"Compactness for computability" - does it ever happen?

asked Sep 20, 2019 at 17:49

19 votes

1 answer

860 views

Automorphism group of the Turing degrees

asked Jan 23, 2013 at 18:38

19 votes

4 answers

1k views

Pathological behavior of Borel sets?

asked Apr 7, 2014 at 5:46

19 votes

0 answers

554 views

What algebraic properties are preserved by $\mathbb{N}\leadsto\beta\mathbb{N}$?

asked Jul 23, 2022 at 0:24

18 votes

1 answer

2k views

Lawvere's fixed point theorem and the Recursion Theorem

asked May 19, 2013 at 22:52

18 votes

1 answer

756 views

Two strengthenings of "strong measure zero"

asked Sep 26, 2015 at 6:29

18 votes

1 answer

1k views

A topological version of the Lowenheim-Skolem number

asked Aug 8, 2021 at 5:19

17 votes

0 answers

1k views

Non-rigid ultrapowers in $\mathsf{ZFC}$?

asked Nov 10, 2021 at 16:01

17 votes

0 answers

436 views

The free complete lattice on three generators, beyond ZF

asked Oct 1, 2021 at 17:56

17 votes

1 answer

605 views

How hard is it to say "not exactly $p$" with a Horn sentence?

asked Feb 20, 2022 at 23:33

17 votes

1 answer

861 views

Positive set theory and the "co-Russell" set

asked May 10, 2020 at 19:18

17 votes

1 answer

752 views

What sets can be unraveled?

asked Aug 28, 2020 at 5:05

Stack Exchange Network

408 Questions

What are some proofs of Godel's Theorem which are essentially different from the original proof?

Counterexamples in universal algebra

Ur-elemental surprises

Godel on recursion-theoretic hierarchies

Supercompact and Reinhardt cardinals without choice

Where do uncountable models collapse to?

On the global structure of the Gromov-Hausdorff metric space

Detecting uncountable cardinals in $(\mathbb{R};+,\times,\mathbb{N})$

Are there infinitely many "generalized triangle vertices"?

Self-containing structures

Undetermined Banach-Mazur games in ZF?

Gently changing measure

Antirandom reals

Relative null-ness

A limit to Shoenfield Absoluteness

Is "almost-solvability" of Diophantine equations decidable?

Does sine interact equationally with addition alone?

Topological universal algebra: what is a variety?

"Compactness for computability" - does it ever happen?

Automorphism group of the Turing degrees

Pathological behavior of Borel sets?

What algebraic properties are preserved by $\mathbb{N}\leadsto\beta\mathbb{N}$?

Lawvere's fixed point theorem and the Recursion Theorem

Two strengthenings of "strong measure zero"

A topological version of the Lowenheim-Skolem number

Non-rigid ultrapowers in $\mathsf{ZFC}$?

The free complete lattice on three generators, beyond ZF

How hard is it to say "not exactly $p$" with a Horn sentence?

Positive set theory and the "co-Russell" set

What sets can be unraveled?