Reference no: EM133033659
Theory of Computation Assignment
Question 1. Consider the following language
INFTM = {(M)|L(M ) is finite}
We are given a TM description as input, and we want to determine if the machine can accept infinitely many strings. Prove that INFTM is undecidable. (Hint: reduce from ATM)
Question 2. Consider the following language.
DISTM = {(M1, M2)|L(M1) ∩ L(M2) = ∅}}
We are given two machines, and we want to check if the machines are disjoint - that is, they don't recognize any of the same strings.
Prove that DISTM is undecidable. (Hint: reduce from ETM. Use the fact that is the only language that is disjoint from Σ∗.)
Question 3. Consider the following language
L = {(M, D)|M is a TM, D is a DFA, L(M ) = L(D)}
We are given a TM description and a DFA description, and we want to determine if the two machines are equivalent. Note that this is different from EQTM because one of the input machines is a DFA. Prove that L is undecidable. (Hint: reduce from ALLTM).
Question 4. This problem is taken from problem 5.22 in Sipser. Prove that a language L is Turing- recognizable if and only if L ≤m ATM. For full credit make sure your proof includes both directions.
Question 5.(a) Prove that if L ≤m L¯ then L¯ ≤m L
(b) Prove that L is Turing-recognizable and L ≤m L¯ then L is decidable.