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Contractible edges in triangle-free graphs
Authors:Yoshimi Egawa  Hikoe Enomoto  Akira Saito
Affiliation:(1) Dept. of Applied Math., Science University of Tokyo, Shinjuku-ku, 162 Tokyo, Japan;(2) Dept. of Information Science Faculty of Science, University of Tokyo, Hongo, Bunkyo-ku, 113 Tokyo, Japan
Abstract:An edge of a graph is calledk-contractible if the contraction of the edge results in ak-connected graph. Thomassen [5] proved that everyk-connected graph of girth at least four has ak-contractible edge. In this paper, we study the distribution ofk-contractible edges in triangle-free graphs and show the following: Whenk≧2, everyk-connected graph of girth at least four and ordern≧3k, hasn+(3/2)k 2-3k or morek-contractible edges.
Keywords:05 C 40
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