Questions tagged [turing-machines]

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6 votes
1 answer
167 views

A variant of the Busy Beaver function

Set $BB(k,n)$ to be the same definition as the Busy Beaver but where one is looking at all $n$-state machines, and the transition graph has at most $k$ "write 1" instructions. This may be a ...
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0 votes
1 answer
86 views

Turing degrees inside the $\Pi_1^0$ class with top Medvedev degree

I'm sure i have read that the following (or something that implies this) is true Let $X$ be a $\Pi_1^0$ class with top Medvedev degree. Then for every $x\in X$, there is $y\in X$ with $y<_T x$. ...
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1 vote
0 answers
60 views

Game with Turing machines

Introduction The following game is quite nice: Alice has, in secret, constructed a polynomial $P \in \mathbb{Z}[x]$. On day $n=1,2,3,...$, she secretly writes down $P(n)$ on a piece of paper. Each day,...
2 votes
1 answer
140 views

Computing the halting problem with no computable bound on the use function

I would like to prove that there are two sets $A,B\subset \mathbb{N}$ such that $A |_T B$ $\emptyset' \equiv_T A\oplus B$ for every $e$, if $\{e\}^{A\oplus B}=\emptyset'$ then the map sending $(B,n)$ ...
  • 192
2 votes
2 answers
499 views

Are ITTM's necessary to compute Turing's "computable numbers" and what does that mean for ordinary recursion theory?

In his celebrated paper, "On Computable Numbers, With An Application To the Entscheidungsproblem", Turing defines a "computable number" as follows: The "computable" ...
26 votes
3 answers
3k views

What sorts of extra axioms might we add to ZFC to compute higher Busy Beaver numbers?

First, some context. Ever since I was a high schooler, I have been fascinated with large numbers. As I have grown in mathematical maturity, I have become both disappointed and fascinated to see that ...
  • 449
2 votes
0 answers
111 views

Is Steiner symmetrization "Turing complete"?

This question stems from intuition so it is a little soft. It concerns performing computation using transformations on sets. The idea is that a rearrangement like Steiner symmetrization might be "...
3 votes
1 answer
577 views

Proof that dynamical systems with bounded Kolmogorov complexity can't emulate all Turing machines

Motivation: During a discussion with neuroscientists the question arose as to whether the human brain may emulate any Turing machine. If we assume that animal brains may be modelled as deterministic ...
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