Questions tagged [universal-turing-machines]

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Asymptotic time required to simulate a Turing machine M for k steps

Problem: Given an encoding of a Turing machine M and a natural number k as input, find the output of M (given a blank tape) after k steps. Wikipedia's page on EXPTIME-complete says it takes O(k) time ...
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2answers
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For a specific unbounded Turing machine, is its Halting problem undecidable?

The question is on the title. To make it clearer, I state some facts. We all know that the Halting problem with input is undecidable. It leads to, given a specific input (e.g. empty string), the ...
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What is the VC dimension of Turing machines with specified maximum size?

Note by "maximum size" in the question I'm referring to the size of the Turing machine's state machine. I chose Turing machines in the question to make the question concrete, but I'm also more ...
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1answer
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About reduction relation between $HP$ and $\mathcal{E}\mbox{*}$ [closed]

I'm studying Theory Of Computation and have some questions in the beginning: About reduction relation between $HP$ and $\mathcal{E}\mbox{*}$ $HP =$ {$<M,w>$ $|$ $M$ is a $TM$ and it halts on ...
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Can Pattern Recognition algorithms be considered Oracle Machines (in the Turing sense)?

I was reading Paul Churchland's "Engine of Reason, Seat of the Soul", where argues that humans (and potentially artificial neural networks as well) are capable of non-Turing computation because they ...
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Where can I find a Turing machine evaluating arithmetic expressions? [closed]

Is there a Turing machine that can evaluate arithmetic operations with brackets containing +, -, and ...
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1answer
639 views

Multi Head universal Turing machine

It is common knowledge that a universal Turing machine can simulate any Turing machine with logarithmic overhead. Is it possible to make this overhead constant by constructing an analogous "Universal" ...
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3answers
396 views

Fastest Turing Machine

Recently I have been reading about Kolmogorov Complexity. As such I started thinking about the "fastest turing machine". In particular I am not interested in finding such a machine, I am only ...
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1answer
263 views

Is my language Turing-complete?

Consider a language like Brainfuck but without the brackets. At the end of each line (i.e. when "\n" occurs), if the current cell is not 0, then the line is re-executed. An example of an infinite ...
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How much smaller can universal Turing machines get if they only need to be universal for a subclass?

Say that a Turing machine $U$ is universal for a class $\mathcal{C}$ of languages if for any language $L \in \mathcal{C}$, there is a word $w_L$ with: $$(\forall w)\quad w \in L \Leftrightarrow U(w_L, ...
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1answer
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Turing degree of Solomonoff semi-measure

We define the Solomonoff semi-measure $m$ on finite strings $x$ by $$m(x) = \sum_{p: U(p) = x} 2^{-l(p)},$$ where $U$ is a universal prefix Turing machine, $U(p) = x$ means $U$ outputs $x$ on input $...
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2answers
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Can we not output the Kolmogorov complexity?

Let us fix a prefix-free encoding of Turing-machines and a universal Turing-machine $U$ that on input $(T,x)$ (encoded as the prefix-free code of $T$ followed by $x$) outputs whatever $T$ outputs on ...
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1answer
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Was bombe machine turing complete?

In the recent movie called The Imitation Game, there is a affirmation that Turing was building his theoretical machine. That machine is the Bombe Machine. Is this machine really equivalent to a Turing ...
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1answer
335 views

Is Kolmogorov complexity a surjective function?

Let us fix an encoding of Turing-machines and a universal Turing-machine, U, that on input (T,x) outputs whatever T outputs on input x (possibly both running forever). Define the Kolmogorov complexity ...
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1answer
228 views

What are different definitions of Universal Turing-machine?

I am not sure what is the appropriate way for this, but I would like to collect different possible definitions/variants of Universal Turing-machines. Here are the ones I know, post below if you know ...