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Evasive random walks and the clairvoyant demon
Author(s) - 
Abrams Aaron, 
Landau Henry, 
Landau Zeph, 
Pommersheim James, 
Zaslow Eric
Publication year - 2002
Publication title - 
random structures and algorithms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.314
H-Index - 69
eISSN - 1098-2418
pISSN - 1042-9832
DOI - 10.1002/rsa.999
Subject(s) - random walk , demon , security token , combinatorics , struct , mathematics , graph , discrete mathematics , computer science , statistics , physics , computer security , quantum mechanics , programming language
A pair of random walks ( R ,  S ) on the vertices of a graph  G  is successful if two tokens moving one at a time can be scheduled (moving only one token at a time) to travel along  R  and  S  without colliding. We consider questions related to P. Winkler's clairvoyant demon problem, which asks whether for random walks  R  and  S  on  G ,  Pr [( R ,  S )is successful] >0. We introduce the notion of an evasive walk on  G : a walk  S  so that for a random walk  R  on  G ,  Pr [( R ,  S )is successful] >0. We characterize graphs  G  having evasive walks, giving explicit constructions on such  G . Also, we show that on a cycle, the tokens must collide quickly with high probability. © 2002 Wiley Periodicals, Inc. Random Struct. Alg. 20: 220–229, 2002
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