Constrained Ramsey Numbers

For two graphs S and T, the constrained Ramsey number f(S, T) is the minimum n such that every edge coloring of the complete graph on n vertices, with any number of colors, has a monochromatic subgraph isomorphic to S or a rainbow (all edges differently colored) subgraph isomorphic to T. The Erdos-Rado Canonical Ramsey Theorem implies that f(S, T) exists if and only if S is a star or T is acyclic, and much work has been done to determine the rate of growth of f(S, T) for various types of parameters. When S and T are both trees having s and t edges respectively, Jamison, Jiang, and Ling showed that f(S, T) <= O(st^2) and conjectured that it is always at most O(st). They also mentioned that one of the most interesting open special cases is when T is a path. In this work, we study this case and show that f(S, P_t) = O(st log t), which differs only by a logarithmic factor from the conjecture. This substantially improves the previous bounds for most values of s and t.Comment: 12 pages; minor revision

Rainbow Generalizations of Ramsey Theory - A Dynamic Survey

In this work, we collect Ramsey-type results concerning rainbow edge colorings of graphs

Rainbow Generalizations of Ramsey Theory - A Dynamic Survey

In this work, we collect Ramsey-type results concerning rainbow edge colorings of graphs

problems in graph theory and probability

This dissertation is a study of some properties of graphs, based on four journal papers (published, submitted, or in preparation). In the first part, a random graph model associated to scale-free networks is studied. In particular, preferential attachment schemes where the selection mechanism is time-dependent are considered, and an infinite dimensional large deviations bound for the sample path evolution of the empirical degree distribution is found. In the latter part of this dissertation, (edge) colorings of graphs in Ramsey and anti-Ramsey theories are studied. For two graphs, G, and H, an edge-coloring of a complete graph is (G;H)-good if there is no monochromatic subgraph isomorphic to G and no rainbow (totally muticolored) subgraph isomorphic to H in this coloring. Some properties of the set of number of colors used by some (G;H)-colorings are discussed. Then the maximum element in this set when H is a cycle is studied

Mono-multi bipartite Ramsey numbers, designs, and matrices

AbstractEroh 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