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Mathematical Notes

, Volume 95, Issue 1–2, pp 245–252 | Cite as

On Turán’s (3,4)-problem with forbidden subgraphs

  • A. A. Razborov
Article

Abstract

We identify three 3-graphs on five vertices that are missing in all known extremal configurations for Turán’s (3,4)-problem and prove Turán’s conjecture for 3-graphs that are additionally known not to contain any induced copies of these 3-graphs. Our argument is based on an (apparently) new technique of “indirect interpretation” that allows us to retrieve additional structure from hypothetical counterexamples to Turán’s conjecture, but in rather loose and limited sense. We also include two miscellaneous calculations in flag algebras that prove similar results about some other additional forbidden subgraphs.

Keywords

Turán’s (3, 4)-problem 3-graph hypergraph forbidden subgraph 

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Copyright information

© Pleiades Publishing, Ltd. 2014

Authors and Affiliations

  • A. A. Razborov
    • 1
    • 2
    • 3
  1. 1.University of ChicagoChicagoUSA
  2. 2.Steklov Mathematical InstituteRussian Academy of SciencesMoscowRussia
  3. 3.Toyota Technological InstituteChicagoUSA

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