What does it mean that some problem is undecidable? For instance the halting problem. Does it mean that humans can never invent a new technique that always decides whether a turing …

28 I read that Presburger arithmetic is decidable while Peano arithmetic is undecidable. Peano arithmetic extends Presburger arithmetic just with the addition of the multiplication operator. …

Aug 18, 2015 · Thus the undecidability of S is decidable which contradicts the assumption that the undecidability of S is undecidable. Thus for any statement S, if its undecidability is …

Jan 15, 2015 · Show that minimal CFG is undecidable (Sipser 5.36) Ask Question Asked 10 years, 9 months ago Modified 5 years ago

Feb 19, 2015 · I wonder how the Collatz conjecture could possibly be undecidable. Let's say it's undecidable, then no counter example can ever be found, and that to me seems to imply that …

So, I need the answer to the question in the title: Are all undecidable problems NP-hard? If I have some undecidable problem (for example, Post correspondence problem), can I say it's NP …

This problem is known to be undecidable and has a nice history (Wang originally gave a decision procedure, but it works only if the tiles form a periodic tiling, while there exists sets which give …

Jan 19, 2023 · P = NP is not known to be a $\Pi_1^0$ statement. But there is a hilarious proof in "On the independence of P versus NP" (1992) that if P vs NP is independent of PA, then NP …

Mar 8, 2011 · What is difference between "recognizable" and "decidable" in context of Turing machines?

May 2, 2017 · 8 In the context of computability theory, there is no difference between a non-computable set and an undecidable set. The term "undecidable" is also used in logic to refer to …