Abstract
Say that a sequenceS 0, ..., Sn has a (global) point of increase atk ifS k is maximal amongS 0, ..., Sk and minimal amongS k, ..., Sn. We give an elementary proof that ann-step symmetric random walk on the line has a (global) point of increase with probability comparable to 1/logn. (No moment assumptions are needed.) This implies the classical fact, due to Dvoretzky, Erdős and Kakutani (1961), that Brownian motion has no points of increase.
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Research partially supported by NSF grant # DMS-9404391.
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Peres, Y. Points of increase for random walks. Israel J. Math. 95, 341–347 (1996). https://doi.org/10.1007/BF02761045
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DOI: https://doi.org/10.1007/BF02761045