Centre for Discrete and Applicable Mathematics

 CDAM Research Report, LSE-CDAM-2006-03

March 2006

Network Search Games With Immobile Hider, Without a Designated Searcher Starting Point

Steve Alpern, Vic Baston and Shmuel Gal

In the (zero-sum) search game Z(G,x) proposed by Isaacs, the Hider picks a point H in the network G and the Searcher picks a unit speed path S(t) in G with S(0)=x. The payoff to the maximizing Hider is the time T=T(S,H)=min{t:S(t)=H} required for the Searcher to find the Hider. An extensive theory of such games has been developed in the literature. This paper considers the related games Z(G), where the requirement S(0)=x is dropped, and the Searcher is allowed to choose his starting point. This game has been solved by Dagan and Gal for the important case where G is a tree, and by Alpern for trees with Eulerian networks attached. Here, we extend those results to a wider class of networks, employing theory initiated by Reijnierse and Potters and completed by Gal, for the fixed-start games Z(G,x).
Our results may be more easily interpreted as determining the best worst-case method of searching a network from an arbitrary starting point.

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