Question

Is this undecidable language recognizable?

score 1.9k · Answer 1 · 2026-03-29 13:20:21

1.9k

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Is this undecidable language recognizable?

Published on 29 Mar 2026 - 13:20

score 615 · Answer 2 · 2026-02-23 19:15:16

615

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An undecidable problem and a non-semidecidable one

Published on 23 Feb 2026 - 19:15

score 33 · Answer 3 · 2020-08-02 20:18:55

33

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if $\ L_{1} \cup L_{2}$ is regular and $\ L_{1} \cap L_{2}$ is regular, and $\ L_{2}$ is regular, so $\ L_{1}$ is regular.

Published on 02 Aug 2020 - 20:18

score 149 · Answer 4 · 2020-08-04 19:54:31

149

Views

The beta-function lemma (in Boolos and Jeffrey) without primes?

Published on 04 Aug 2020 - 19:54

score 242 · Answer 5 · 2026-04-01 01:35:17

242

Views

Proving Rice's theorem using Kleene's fixed point theorem

Published on 01 Apr 2026 - 1:35

score 197 · Answer 6 · 2026-03-29 13:23:24

197

Views

Undecidability of the Halting Problem excluding the main diagonal

Published on 29 Mar 2026 - 13:23

score 119 · Answer 7 · 2020-08-12 04:23:13

119

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What is the full definition of the head position “inferior limits” rule for Ordinal Turing Machines?

Published on 12 Aug 2020 - 4:23

score 116 · Answer 8 · 2026-03-29 13:22:59

116

Views

Can a Busy Beaver have duplicate transitions

Published on 29 Mar 2026 - 13:22

score 183 · Answer 9 · 2020-08-15 22:46:15

183

Views

Is $P=\{x\in\mathbb{R}_+: n\mapsto\lfloor nx\rfloor\text{ is a p.r.f.}\}$ closed under addition?

Published on 15 Aug 2020 - 22:46

score 107 · Answer 10 · 2020-08-16 22:24:58

107

Views

Do the recursively enumerable sets form a coverage for $\mathbb{N}$? If yes, which additional saturation conditions does it satisfy?

Published on 16 Aug 2020 - 22:24

score 175 · Answer 11 · 2026-03-25 11:09:59

175

Views

Primitive recursive predicates for exponentiation and multiplication

Published on 25 Mar 2026 - 11:09

score 388 · Answer 12 · 2026-02-23 01:46:31

388

Views

Show the original Ackermann function is non-primitive recursive

Published on 23 Feb 2026 - 1:46

score 408 · Answer 13 · 2026-03-29 07:22:20

408

Views

Provably total functions in $\mathsf{Q}$

Published on 29 Mar 2026 - 7:22

score 169 · Answer 14 · 2026-03-25 13:54:10

169

Views

Can all $\mathsf{Q}$-provably recursive functions be "frequently termlike"?

Published on 25 Mar 2026 - 13:54

score 36 · Answer 15 · 2020-08-24 21:52:30

36

Views

Question in the Proof of the Recursion theorem - why is $d(u)$ total Recursive?

Published on 24 Aug 2020 - 21:52

List Question

Is this undecidable language recognizable?

An undecidable problem and a non-semidecidable one

if $\ L_{1} \cup L_{2}$ is regular and $\ L_{1} \cap L_{2}$ is regular, and $\ L_{2}$ is regular, so $\ L_{1}$ is regular.

The beta-function lemma (in Boolos and Jeffrey) without primes?

Proving Rice's theorem using Kleene's fixed point theorem

Undecidability of the Halting Problem excluding the main diagonal

What is the full definition of the head position “inferior limits” rule for Ordinal Turing Machines?

Can a Busy Beaver have duplicate transitions

Is $P=\{x\in\mathbb{R}_+: n\mapsto\lfloor nx\rfloor\text{ is a p.r.f.}\}$ closed under addition?

Do the recursively enumerable sets form a coverage for $\mathbb{N}$? If yes, which additional saturation conditions does it satisfy?

Primitive recursive predicates for exponentiation and multiplication

Show the original Ackermann function is non-primitive recursive

Provably total functions in $\mathsf{Q}$

Can all $\mathsf{Q}$-provably recursive functions be "frequently termlike"?

Question in the Proof of the Recursion theorem - why is $d(u)$ total Recursive?

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