Question

In: Computer Science

Prove whether the set of all proofs within any formal system is decidable, recognizable, or unrecognizable

Prove whether the set of all proofs within any formal system is decidable, recognizable, or unrecognizable

Solutions

Expert Solution

A Turing machine M is said to recognize a language L if L = L(M).
A Turing machine M is said to decide a language L if L = L(M)
and M halts on every input.
L is said to be Turing-recognizable (Recursively Enumerable (R.E.)
or simply recognizable) if there exists a TM M which recognizes L.
L is said to be Turing-decidable (Recursive or simply decidable) if
there exists a TM M which decides L.

But not all languages are decidable! We will show:
Atm = {<M,w >|M is a TM and M accepts w } is undecidable.
However Atm is Turing-recognizable!

the answer has been provided below:


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