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random walk on hypercube

Source: miklos schweitzer 1997 q10

September 28, 2021
probability and statsMiklos Schweitzer

Problem Statement

Assign independent standard normally distributed random variables to the vertices of an n-dimensional cube. Say one vertex is greater than another if the assigned number is greater. Define a random walk on the vertices according to the following rules: a) the starting point is chosen from all the vertices with equal probability, b) during our journey, if we reach a vertex such that there are adjacent vertices which have higher values, we choose the next vertex with equal probability, c) if there is none, we stop. Prove that ε>0Kn>1\forall\varepsilon>0 \,\exists K\, \forall n>1 P(λ>Klogn)<εP(\lambda> K \log n) <\varepsilon where λ\lambda is the number of steps of the random walk.