The Clairvoyant Demon Has a Hard Task

  • Authors:
  • Peter Gács

  • Affiliations:
  • Computer Science Department, Boston University, Boston, MA 02215-2411, USA (e-mail: gacs@bu.edu)

  • Venue:
  • Combinatorics, Probability and Computing
  • Year:
  • 2000

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Abstract

Consider the integer lattice L = ℤ2. For some m ≥ 4, let us colour each column of this lattice independently and uniformly with one of m colours. We do the same for the rows, independently of the columns. A point of L will be called blocked if its row and column have the same colour. We say that this random configuration percolates if there is a path in L starting at the origin, consisting of rightward and upward unit steps, avoiding the blocked points. As a problem arising in distributed computing, it has been conjectured that for m ≥ 4 the configuration percolates with positive probability. This question remains open, but we prove that the probability that there is percolation to distance n but not to infinity is not exponentially small in n. This narrows the range of methods available for proving the conjecture.