358 research outputs found
How far can Nim in disguise be stretched?
A move in the game of nim consists of taking any positive number of tokens
from a single pile. Suppose we add the class of moves of taking a nonnegative
number of tokens jointly from all the piles. We give a complete answer to the
question which moves in the class can be adjoined without changing the winning
strategy of nim. The results apply to other combinatorial games with unbounded
Sprague-Grundy function values. We formulate two weakened conditions of the
notion of nim-sum 0 for proving the results.Comment: To appear in J. Combinatorial Theory (A
-actions of Baumslag-Solitar groups on
Let be the solvable Baumslag-Solitar
group, where . It is known that B(1, n) is isomorphic to the group
generated by the two affine maps of the line : and . The action on S^1 = \RR \cup {\infty} generated by these two affine
maps and is called the standard affine one. We prove that any
representation of BS(1,n) into is (up to a finite index subgroup)
semiconjugated to the standard affine action
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