User Joel David Hamkins

28 votes

Strong induction without a base case

answered Jan 17, 2010 at 1:39

28 votes

Accepted

Is the sum of 2 Lebesgue measurable sets measurable?

answered Mar 26, 2010 at 22:52

28 votes

How many orders of infinity are there?

answered Jun 27, 2010 at 1:44

28 votes

Why is Cohen's result insufficient to settle CH?

answered Jun 20, 2010 at 12:54

28 votes

Non-Borel sets without axiom of choice

answered Jul 21, 2010 at 0:30

28 votes

Accepted

What is the generic poset used in forcing, really?

answered Jan 5, 2011 at 14:35

28 votes

Using Busy Beavers to prove conjectures

answered Jan 4 at 14:59

27 votes

Accepted

Writing a function on $\mathbb{R}$ as a sum of two injections

answered Nov 26, 2023 at 0:02

27 votes

Is it possible to make an algorithm that could predict the likelihood that a program will halt?

answered Dec 1, 2015 at 0:48

27 votes

Accepted

Why is there no Borel function mapping every countable set of reals outside itself?

answered Nov 24, 2010 at 4:10

27 votes

Does Cantor-Bernstein hold for classes?

answered Sep 6, 2010 at 20:30

27 votes

Accepted

Jonsson Boolean algebras?

answered Jul 11, 2011 at 17:33

27 votes

Are there examples of statements that have been proven whose consistency proofs came before their proofs?

answered Jul 25, 2011 at 10:03

27 votes

Infinite CPU clock rate and hotel Hilbert

answered Apr 21, 2010 at 11:02

27 votes

Accepted

On statements independent of ZFC + V=L

answered Jan 12, 2010 at 2:14

27 votes

Accepted

Are there any good nonconstructive "existential metatheorems"?

answered Nov 20, 2009 at 14:19

27 votes

Analogues of P vs. NP in the history of mathematics

answered Mar 13, 2014 at 23:27

27 votes

Accepted

I know that you know...

answered Nov 23, 2012 at 18:01

26 votes

Godel's incompleteness: can the diagonalization be done in computation rather than logic?

answered Jun 4, 2012 at 13:12

26 votes

Is there any research on set theory without extensionality axiom?

answered May 27, 2014 at 12:21

26 votes

Accepted

What does it mean for a mathematical statement to be true?

answered May 12, 2010 at 13:07

26 votes

Forcing as a tool to prove theorems

answered Jun 29, 2010 at 18:41

26 votes

How would one even begin to try to prove that a simple number-theoretic statement is undecidable?

answered Jun 11, 2010 at 20:59

26 votes

Why relativization can't solve NP !=P?

answered Aug 15, 2010 at 17:16

26 votes

Siegel zeros and other "illusory worlds": building theories around hypotheses believed to be false

answered Jul 15, 2021 at 12:19

26 votes

Accepted

"Natural" undecidable problems not reducible to the halting problem

answered Dec 26, 2022 at 15:54

26 votes

Accepted

Is multiplication implicitly definable from successor?

answered Jul 9, 2022 at 16:44

26 votes

Accepted

Are classes still "larger" than sets without the axiom of choice?

answered Apr 30, 2018 at 23:02

26 votes

Quantifier complexity of the definition of continuity of functions

answered Aug 20, 2023 at 23:18

25 votes

Accepted

How (non-)computable is set theory?

answered Jun 27, 2018 at 23:01

Stack Exchange Network

1,913 Answers

Strong induction without a base case

Is the sum of 2 Lebesgue measurable sets measurable?

How many orders of infinity are there?

Why is Cohen's result insufficient to settle CH?

Non-Borel sets without axiom of choice

What is the generic poset used in forcing, really?

Using Busy Beavers to prove conjectures

Writing a function on $\mathbb{R}$ as a sum of two injections

Is it possible to make an algorithm that could predict the likelihood that a program will halt?

Why is there no Borel function mapping every countable set of reals outside itself?

Does Cantor-Bernstein hold for classes?

Jonsson Boolean algebras?

Are there examples of statements that have been proven whose consistency proofs came before their proofs?

Infinite CPU clock rate and hotel Hilbert

On statements independent of ZFC + V=L

Are there any good nonconstructive "existential metatheorems"?

Analogues of P vs. NP in the history of mathematics

I know that you know...

Godel's incompleteness: can the diagonalization be done in computation rather than logic?

Is there any research on set theory without extensionality axiom?

What does it mean for a mathematical statement to be true?

Forcing as a tool to prove theorems

How would one even begin to try to prove that a simple number-theoretic statement is undecidable?

Why relativization can't solve NP !=P?

Siegel zeros and other "illusory worlds": building theories around hypotheses believed to be false

"Natural" undecidable problems not reducible to the halting problem

Is multiplication implicitly definable from successor?

Are classes still "larger" than sets without the axiom of choice?

Quantifier complexity of the definition of continuity of functions

How (non-)computable is set theory?