Chapter 0: Q22P (page 1)
Use the result of Problem 6.21 to give a function f that is computable with an oracle for ATM, where for each n,f(n) is an incompressible string of length n.
Short Answer
The given statement is proved.
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Chapter 0: Q22P (page 1)
Use the result of Problem 6.21 to give a function f that is computable with an oracle for ATM, where for each n,f(n) is an incompressible string of length n.
The given statement is proved.
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A two-dimensional finite automaton (2DIM-DFA) is defined as follows. The input is an rectangle, for any m,n. The squares along the boundary of the rectangle contain the symbol # and the internal squares contain symbols over the input alphabet . The transition function indicates the next state and the new head position (Left, Right, Up, Down). The machine accepts when it enters one of the designated accept states. It rejects if it tries to move off the input rectangle or if it never halts. Two such machines are equivalent if they accept the same rectangles. Consider the problem of determining whether two of these machines are equivalent. Formulate this problem as a language and show that it is undecidable.
Use the results of Exercise to give another proof that every regular language is context- free, by showing how to convert a regular expression directly to an equivalent context-free grammar.
Recall, in our discussion of the Church–Turing thesis, that we introduced the language is a polynomial in several variables having an integral root}. We stated, but didn’t prove, thatis undecidable. In this problem, you are to prove a different property of—namely, thatis -hard. A problem is -hard if all problems in are polynomial time reducible to it, even though it may not be initself. So you must show that all problems in are polynomial time reducible to .
Read the informal definition of the finite state transducer given in Exercise 1.24. Give the state diagram of an FST with the following behaviour. Its input and output alphabets are . Its output string is identical to the input string on the even positions but inverted on the odd positions. For example, on input 0000111 it should output 1010010 .
Consider the problem of determining whether a Turing machine on an input w ever attempts to move its head left at any point during its computation on . Formulate this problem as a language and show that it is decidable.
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