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A note on the size Ramsey numbers for matchings versus cycles

Edy Tri BaskoroTomáš Vetrík — 2021

Mathematica Bohemica

For graphs G , F 1 , F 2 , we write G ( F 1 , F 2 ) if for every red-blue colouring of the edge set of G we have a red copy of F 1 or a blue copy of F 2 in G . The size Ramsey number r ^ ( F 1 , F 2 ) is the minimum number of edges of a graph G such that G ( F 1 , F 2 ) . Erdős and Faudree proved that for the cycle C n of length n and for t 2 matchings t K 2 , the size Ramsey number r ^ ( t K 2 , C n ) < n + ( 4 t + 3 ) n . We improve their upper bound for t = 2 and t = 3 by showing that r ^ ( 2 K 2 , C n ) n + 2 3 n + 9 for n 12 and r ^ ( 3 K 2 , C n ) < n + 6 n + 9 for n 25 .

On Ramsey ( K 1 , 2 , C ) -minimal graphs

Tomás VetríkLyra YuliantiEdy Tri Baskoro — 2010

Discussiones Mathematicae Graph Theory

For graphs F, G and H, we write F → (G,H) to mean that any red-blue coloring of the edges of F contains a red copy of G or a blue copy of H. The graph F is Ramsey (G,H)-minimal if F → (G,H) but F* ↛ (G,H) for any proper subgraph F* ⊂ F. We present an infinite family of Ramsey ( K 1 , 2 , C ) -minimal graphs of any diameter ≥ 4.

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