Chapter 5: 3E (page 239)
Find a match in the following instance of the Post Correspondence Problem.
Short Answer
The required match is
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Chapter 5: 3E (page 239)
Find a match in the following instance of the Post Correspondence Problem.
The required match is
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Show that is a transitive relation?
Let be the tape alphabet for all in this problem. Define the busy beaver function as follows. For each value of , consider all -state that halt when started with a blank tape. Let be the maximum number of that remain on the tape among all of these machines. Show that is not a computable function.
Show that is undecidable.
Define a two-headed finite automaton (2DFA) to be a deterministic finite automaton that has two read-only, bidirectional heads that start at the left-hand end of the input tape and can be independently controlled to move in either direction. The tape of a 2DFA is finite and is just large enough to contain the input plus two additional blank tape cells, one on the left-hand end and one on the right-hand end, that serve as delimiters. A 2DFA accepts its input by entering a special accept state. For example, a 2DFA can recognize the language .
Question: Let be the tape alphabet for all TMs in this problem. Define the busy beaver function as follows. For each value of k, consider all K-state TMs that halt when started with a blank tape. Let be the maximum number of 1s that remain on the tape among all of these machines. Show that BB is not a computable function.
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