Title
A Note on Busy Beavers and Other Creatures
Abstract
Consider Turing machines that read and write the symbols 1 and 0 on a one-dimensional tape that is infinite in both directions, and halt when started on a tape containing all O's. Rado'sbusy beaver function ones(n) is the maximum number of 1's such a machine, withn states, may leave on its tape when it halts. The function ones(n) is noncomputable; in fact, it grows faster than any computable function. Other functions with a similar nature can also be defined. The function time(n) is the maximum number of moves such a machine may make before halting. The function num(n) is the largest number of 1's such a machine may leave on its tape in the form of a single run; and the function space(n) is the maximum number of tape squares such a machine may scan before it halts. This paper establishes a variety of bounds on these functions in terms of each other; for example, time(n) ≤ (2n − 1) × ones(3n + 3). In general, we compare the growth rates of such functions, and discuss the problem of characterizing their growth behavior in a more precise way than that given by Rado.
Year
DOI
Venue
1996
10.1007/BF01192693
Mathematical Systems Theory
Keywords
Field
DocType
Turing Machine,Computable Function,Bell System Technical Journal,Marked Zone,Blank Tape
Creatures,Discrete mathematics,Combinatorics,Busy beaver,Computer science,Turing machine,Multitape Turing machine,Beaver,Computable function
Journal
Volume
Issue
ISSN
29
4
0025-5661
Citations 
PageRank 
References 
2
0.46
3
Authors
3
Name
Order
Citations
PageRank
Amir M Ben-Amram132730.52
Bryant A. Julstrom237645.64
Uri Zwick33586257.02