Undecidability of the Emptiness Problem for Turing Machines

This paper demonstrates that the E_TM problem, which asks whether a Turing machine's language is empty, is undecidable. The proof involves assuming decidability and deriving a contradiction by constructing a decider for the known undecidable A_TM problem.

Undecidability of the Emptiness Problem for Turing Machines
Easy Theory
23.7K views • Jan 18, 2021
Undecidability of the Emptiness Problem for Turing Machines

About this video

Here we show that the E_TM problem is undecidable. We suppose that it were decidable, then construct a decider for the A_TM problem, which cannot possibly exist. The key idea is to make a new machine that has empty language iff M accepts w.

What is a Turing Machine? It is a state machine that has a set of states, input, tape alphabet, a start state, exactly one accept state, and exactly one reject state. See https://www.youtube.com/watch?v=j0bIxPqlYLE&ab_channel=EasyTheory for more details.

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23.7K

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417

Duration

9:00

Published

Jan 18, 2021

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