User Peter Gerdes

26 votes

2 answers

2k views

Decidability of 3 body problem

asked Oct 16, 2021 at 14:31

10 votes

1 answer

501 views

What is the least $\alpha$ such that $L_\alpha$ contains a non-measurable set

asked Sep 10 at 23:59

9 votes

1 answer

849 views

Practical Benefits of HTT/univalent foundations for assisted proofs

asked Jun 1, 2021 at 17:46

8 votes

1 answer

399 views

Good source for admissible set theory?

asked Apr 28, 2023 at 20:02

7 votes

2 answers

230 views

Why does Weihrauch reducibility make use of multi-functions?

asked Apr 1 at 21:17

7 votes

1 answer

166 views

2-REA PA degrees

asked May 11, 2021 at 20:48

7 votes

0 answers

221 views

$\Pi^0_2$ singleton of minimal arithmetic degree?

asked May 11, 2022 at 4:07

7 votes

1 answer

156 views

Join Density in R.E. Degrees: Are there r.e. B, C with all r.e. X below B computable or C join X computes B

asked May 15, 2018 at 15:40

6 votes

0 answers

248 views

$\omega$-models of $\mathbf{\Sigma^1_1}-DC$ and $\mathbf{\Delta^1_1}-CA$

asked Jan 12, 2013 at 4:31

6 votes

2 answers

278 views

Extending polynomial hierarchy above $\omega$

asked Sep 24 at 3:55

6 votes

3 answers

444 views

Is $0^{(\omega)}$ a minimal cover in the arithmetic degrees

asked Mar 23, 2023 at 4:30

5 votes

0 answers

215 views

Status of Problems in 102 problems in mathematical logic

asked Aug 9, 2023 at 8:27

5 votes

0 answers

192 views

Complexity implications on computability

asked Nov 7, 2023 at 18:40

5 votes

1 answer

170 views

Given B,C incomplete, incomparable r.e. sets must C compute low r.e. set avoiding cone below B? (ADDED: Uniformly?)

asked Jan 5, 2019 at 8:53

5 votes

1 answer

198 views

Does every cuppable r.e. set cup with a low set?

asked Oct 22, 2021 at 1:26

4 votes

1 answer

572 views

Definition of HYP in $L_{\omega_1^{CK}}[a]$?

asked Jan 12, 2013 at 4:35

4 votes

1 answer

422 views

Model of PA with false $\Sigma^0_1$ sentence but no false Con sentence?

asked Jul 19, 2020 at 22:09

4 votes

2 answers

472 views

Infinite descending chain of Turing jumps with equality

asked Dec 11, 2020 at 6:43

4 votes

1 answer

534 views

Complexity of |a| < |b| for ordinal notations?

asked Jun 4, 2023 at 11:36

4 votes

1 answer

71 views

Effectively non-arithmetic $\omega$-REA degrees

asked May 2, 2023 at 4:08

4 votes

2 answers

134 views

Properties of all relatively computable branches

asked Oct 1 at 23:24

3 votes

0 answers

146 views

Lower Bound of Solutions to P=NP?

asked Sep 23 at 21:56

3 votes

1 answer

92 views

Does every arithmetic degree below $0^\omega$ have a representative computable in $0^\omega$?

asked Apr 19, 2023 at 12:42

3 votes

1 answer

134 views

A $\Pi^0_1$ class of $\alpha$-subgenerics for all $\alpha < w_1^{CK}$

asked Aug 11, 2023 at 8:48

3 votes

1 answer

55 views

Does degree of jump determine degrees of relatively r.e. sets?

asked Jul 10, 2020 at 16:52

3 votes

2 answers

148 views

Cupping and capping for 0’ relative to a recursively enumerable set

asked Jul 11, 2020 at 4:00

3 votes

1 answer

226 views

Adding sort of sets over theory with multiple sorts?

asked Nov 21, 2022 at 6:26

2 votes

3 answers

140 views

Incompatible degrees $a,b$ s.t. $x < a$ implies $x \leq b$

asked Mar 15, 2023 at 1:54

2 votes

0 answers

40 views

Uniformity of splitting for n-REA degrees

asked Sep 9, 2022 at 4:17

2 votes

0 answers

235 views

Is computability theory less cumulative than other areas in mathematics?

asked Oct 14, 2022 at 0:45

Stack Exchange Network

62 Questions

Decidability of 3 body problem

What is the least $\alpha$ such that $L_\alpha$ contains a non-measurable set

Practical Benefits of HTT/univalent foundations for assisted proofs

Good source for admissible set theory?

Why does Weihrauch reducibility make use of multi-functions?

2-REA PA degrees

$\Pi^0_2$ singleton of minimal arithmetic degree?

Join Density in R.E. Degrees: Are there r.e. B, C with all r.e. X below B computable or C join X computes B

$\omega$-models of $\mathbf{\Sigma^1_1}-DC$ and $\mathbf{\Delta^1_1}-CA$

Extending polynomial hierarchy above $\omega$

Is $0^{(\omega)}$ a minimal cover in the arithmetic degrees

Status of Problems in 102 problems in mathematical logic

Complexity implications on computability

Given B,C incomplete, incomparable r.e. sets must C compute low r.e. set avoiding cone below B? (ADDED: Uniformly?)

Does every cuppable r.e. set cup with a low set?

Definition of HYP in $L_{\omega_1^{CK}}[a]$?

Model of PA with false $\Sigma^0_1$ sentence but no false Con sentence?

Infinite descending chain of Turing jumps with equality

Complexity of |a| < |b| for ordinal notations?

Effectively non-arithmetic $\omega$-REA degrees

Properties of all relatively computable branches

Lower Bound of Solutions to P=NP?

Does every arithmetic degree below $0^\omega$ have a representative computable in $0^\omega$?

A $\Pi^0_1$ class of $\alpha$-subgenerics for all $\alpha < w_1^{CK}$

Does degree of jump determine degrees of relatively r.e. sets?

Cupping and capping for 0’ relative to a recursively enumerable set

Adding sort of sets over theory with multiple sorts?

Incompatible degrees $a,b$ s.t. $x < a$ implies $x \leq b$

Uniformity of splitting for n-REA degrees

Is computability theory less cumulative than other areas in mathematics?