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New isolated toughness condition for fractional -critical graphs

Volume 147 / 2017

Wei Gao, Weifan Wang Colloquium Mathematicum 147 (2017), 55-65 MSC: Primary 05C70. DOI: 10.4064/cm6713-8-2016 Published online: 8 December 2016

Abstract

Let i(G) be the number of isolated vertices in a graph G. The isolated toughness of G is defined as I(G)=\infty if G is complete, and I(G)=\operatorname{min}\{|S|/i(G-S) : S\subseteq V(G),\, i(G-S)\ge 2\} otherwise. We show that G is a fractional (g,f,n)-critical graph if I(G)\ge (b^{2}+bn-\varDelta )/{a}, where a, b are positive integers, 1\le a\le b, b\ge 2, and \varDelta =b-a. Furthermore, a new isolated toughness condition for fractional (a,b,n)-critical graphs is given.

Authors

  • Wei GaoSchool of Information Science and Technology
    Yunnan Normal University
    Kunming 650500, China
    e-mail
  • Weifan WangDepartment of Mathematics
    Zhejiang Normal University
    Jinhua 321004, China
    e-mail

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