Multicolor Ramsey Properties of Random Graphs and Hypergraphs
First we focus on the size-Ramsey number of a path Pn on n vertices. In particular, we show that 5n/2−15/2≤ˆr(Pn)≤74n for n sufficiently large. This improves the previous lower bound due to Bollobás, and the upper bound due to Letzter. Next we study long monochromatic paths in edge-colored random graph G(n,p) with pn→∞. Recently, Letzter showed that a.a.s. any 2-edge coloring of G(n,p) yields a monochromatic path of length (2/3−o(1))n, which is optimal. Extending this result, we show that a.a.s. any 3-edge coloring of G(n,p) yields a monochromatic path of length (1/2−o(1))n, which is also optimal. We will also discuss this problem for an arbitrary number of colors. We also consider a related problem and show that for any r≥2, a.a.s. any r-edge coloring of G(n,p) yields a monochromatic connected subgraph on (1/(r−1)−o(1))n vertices, which is also tight. Finally, we discuss some extensions of the above results for random hypergraphs.
This is a joint work with Paweł Prałat and also with Patrick Bennett, Louis DeBiasio, and Sean English.