, Volume 12, Issue 2, pp 179–192 | Cite as

Perfect couples of graphs

  • János Körner
  • Gábor Simonyi
  • Zsolt Tuza


We generalize the concept of perfect graphs in terms of additivity of a functional called graph entropy. The latter is an information theoretic functional on a graphG with a probability distributionP on its vertex set. For any fixedP it is sub-additive with respect to graph union. The entropy of the complete graph equals the sum of those ofG and its complement G iffG is perfect. We generalize this recent result to characterize all the cases when the sub-additivity of graph entropy holds with equality.

AMS subject classification code (1991)

05 C 75 94 A 17 05 C 15 94 A 15 


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Copyright information

© Akadémiai Kiadó 1992

Authors and Affiliations

  • János Körner
    • 1
  • Gábor Simonyi
    • 1
  • Zsolt Tuza
    • 2
  1. 1.Mathematical Institute of the Hungarian Academy of SciencesBudapestHungary
  2. 2.Computer and Automation Institute of the Hungarian Academy of SciencesBudapestHungary

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