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I'm having trouble with this problem as I haven't discovered a good way to determine the power of a Turing machine. I was under the impression that if a Turing machine can perform the same actions and satifies unrestricted access to unlimited memory they're all pretty much equivalent. Such as multiple tapes and nondeterministic Turing machines.

I am to determine if a and b are equal, more powerful or less powerful then a single-tape Turing machine. Where do I start?

a) A Turing Machine that can only make moves to the right and never left.

b) A Turing Machine that can move right one space or move left two spaces.

David Richerby
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Yawn
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1 Answers1

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I was under the impression that if a Turing machine can perform the same actions and satifies unrestricted access to unlimited memory they're all pretty much equivalent.

Hint 1: So your first step should be to determine whether a and b have, or can obtain, unrestricted access to unlimited memory.

Hint 2: If yes, then try to emulate the missing pieces of your preferred Turing machine model.

Hint 3: If no, then try to show that the halting problem (with empty tape as input) is decidable.

Thomas Klimpel
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