Abstract
Let t be an integer, f(n) a function, and H a graph. Define the t-Ramsey-Turán number of H, RT t (n,H, f(n)), to be the maximum number of edges in an n-vertex, H-free graph G with α t (G) ≤ f(n), where α t (G) is the maximum number of vertices in a K t -free induced subgraph of G. Erdős, Hajnal, Simonovits, Sós and Szemerédi [6] posed several open questions about RT t (n,K s , o(n)), among them finding the minimum ℓ such that RT t (n,K t+ℓ , o(n)) = Ω(n 2), where it is easy to see that RT t (n,K t+1, o(n)) = o(n 2). In this paper, we answer this question by proving that RT t (n,K t+2, o(n)) = Ω(n 2); our constructions also imply several results on the Ramsey-Turán numbers of hypergraphs.
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This material is based upon work supported by NSF CAREER Grant DMS-0745185, UIUC Campus Research Board Grants 11067, 09072 and 08086, and OTKA Grant K76099.
Work supported by 2010 REGS Program of the University of Illinois and the National Science Foundation through a fellowship funded by the grant DMS 0838434 “EMSW21MCTP: Research Experience for Graduate Students”.
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Balogh, J., Lenz, J. On the Ramsey-Turán numbers of graphs and hypergraphs. Isr. J. Math. 194, 45–68 (2013). https://doi.org/10.1007/s11856-012-0076-2
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DOI: https://doi.org/10.1007/s11856-012-0076-2