Mono-multi bipartite Ramsey numbers, designs, and matrices

  • Authors:
  • Paul N. Balister;András Gyárfás;Jenö Lehel;Richard H. Schelp

  • Affiliations:
  • Department of Mathematical Sciences, The University of Memphis, Memphis, TN;Computer and Automation Research Inst., Hungarian Academy of Sciences, Budapest, Hungary;Department of Mathematical Sciences, The University of Memphis, Memphis, TN;Department of Mathematical Sciences, The University of Memphis, Memphis, TN

  • Venue:
  • Journal of Combinatorial Theory Series A
  • Year:
  • 2006

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Abstract

Eroh and Oellermann defined BRR(G1, G2) as the smallest N such that any edge coloring of the complete bipartite graph KN, N contains either a monochromatic G1 or a multicolored G2. We restate the problem of determining BRR(K1,λ, Kr,s) in matrix form and prove estimates and exact values for several choices of the parameters. Our general bound uses Füredi's result on fractional matchings of uniform hypergraphs and we show that it is sharp if certain block designs exist. We obtain two sharp results for the case r = s = 2: we prove BRR(K1,λ, K2,2) = 3λ - 2 and that the smallest n for which any edge coloring of Kλ,n contains either a monochromatic K1,λ or a multicolored K2,2 is λ2.