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Scaling in Tournaments

E. Ben-Naim, S. Redner, F. Vazquez

cond-mat.stat-mecharXiv:cond-mat/0607694

Abstract

We study a stochastic process that mimics single-game elimination tournaments. In our model, the outcome of each match is stochastic: the weaker player wins with upset probability q<=1/2, and the stronger player wins with probability 1-q. The loser is eliminated. Extremal statistics of the initial distribution of player strengths governs the tournament outcome. For a uniform initial distribution of strengths, the rank of the winner, x*, decays algebraically with the number of players, N, as x* ~ N(-beta). Different decay exponents are found analytically for sequential dynamics, betaseq=1-2q, and parallel dynamics, betapar=1+[ln (1-q)]/[ln 2]. The distribution of player strengths becomes self-similar in the long time limit with an algebraic tail. Our theory successfully describes statistics of the US college basketball national championship tournament.

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