The Range of a Simple Random Walk on Z: An Elementary Combinatorial Approach

Bernhard Moser
unpublished
Two different elementary approaches for deriving an explicit formula for the distribution of the range of a simple random walk on Z of length n are presented. Both of them rely on Hermann Weyl's discrepancy norm, which equals the maximal partial sum of the elements of a sequence. By this the original combinatorial problem on Z can be turned into a known path-enumeration problem on a bounded lattice. The solution is provided by means of the adjacency matrix Q d of the walk on a bounded lattice
more » ... , 1,. .. , d). The second approach is algebraic in nature, and starts with the adjacency matrix Q d. The powers of the adjacency matrix are expanded in terms of products of non-commutative left and right shift matrices. The representation of such products by means of the discrepancy norm reveals the solution directly.
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