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Comment by mwenge

3 months ago

It is indeed proven and the reason they're called Turing machines! https://en.wikipedia.org/wiki/Halting_problem

Doesn't the discovery of the fifth Busy Beaver value indicate that there is a decider for 5-state Turing machines?

  • Yes, there are deciders for all finite sets of TMs. You just cannot have one for all TMs.

    • I think actually for relatively small n we get cases where mathematics says nope, you can't decide that, the machine goes recursive and so now your decider may be looking at a machine which is itself running deciders and Kurt Gödel says "No".

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  • Yes. But there is no decider for n-state Turing machines that works regardless of n.