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Angel Problem


In a game proposed by J. H. Conway, a devil chases an angel on an infinite chessboard. At each move, the devil can eliminate one of the squares, and the angel can make a leap in any direction, covering a distance of at most n squares. Here, n is a positive integer previously fixed, and is called the "power" of the angel. The devil's aim is to trap the angel on an island surrounded by a hole of width at least n.

Can the angel indefinitely escape the devil, if his power is sufficiently high? Can the devil defeat an angel of any finite power? In 2006, Brian Bowditch proved that the 4-angel can win. Later that year, András Máthé proved the 2-angel will win, completely solving the problem.


This entry contributed by Margherita Barile

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References

Conway, J. "The Angel Problem." In Games of No Chance, Proc. MSRI Workshop on Combinatorial Games, July, 1994 (Ed. R. J. Nowakowski.) Cambridge, England: Cambridge University Press, pp. 3-12, 1996. http://www.msri.org/publications/books/Book29/files/conway.pdf.

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Angel Problem

Cite this as:

Barile, Margherita. "Angel Problem." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/AngelProblem.html

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