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On the sum of the reciprocals of cycle lengths in sparse graphs
Authors:A Gyárfás  H J Prömel  B Voigt  E Szemerédi
Institution:1. Computer and Automation Institute of the Hungarian Academy of Sciences, Kende u. 13-17, 1111, Hungary
2. Fakult?t für Mathematik, Universit?t Bielefeld, 4800, Bielefeld 1, West Germany
3. Mathematical Institute of the Hungarian Academy of Sciences, P.O.B. 127, 1364, Budapest, Hungary
Abstract:For a graphG let ℒ(G)=Σ{1/k contains a cycle of lengthk}. Erdős and Hajnal 1] introduced the real functionf(α)=inf {ℒ (G)|E(G)|/|V(G)|≧α} and suggested to study its properties. Obviouslyf(1)=0. We provef (k+1/k)≧(300k logk)−1 for all sufficiently largek, showing that sparse graphs of large girth must contain many cycles of different lengths.
Keywords:05 C 38  05 C 05
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