### Abstract

Jim Propp's P-machine, also known as the 'rotor router model', is a simple deterministic process that simulates a random walk on a graph. Instead of distributing chips to randomly chosen neighbors, it serves the neighbors in a fixed order. We investigate how well this process simulates a random walk. For the graph being the infinite path, we show that, independent of the starting configuration, at each time and on each vertex, the number of chips on this vertex deviates from the expected number of chips in the random walk model by at most a constant c_{1}, which is approximately 2.29. For intervals of length L, this improves to a difference of O (log L), for the L_{2} average of a contiguous set of intervals even to O (sqrt(log L)). All these bounds are tight.

Original language | English |
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Pages (from-to) | 2072-2090 |

Number of pages | 19 |

Journal | European Journal of Combinatorics |

Volume | 28 |

Issue number | 8 |

DOIs | |

Publication status | Published - Nov 1 2007 |

### ASJC Scopus subject areas

- Discrete Mathematics and Combinatorics

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## Cite this

*European Journal of Combinatorics*,

*28*(8), 2072-2090. https://doi.org/10.1016/j.ejc.2007.04.018