A lower bound for set-coloring Ramsey numbers.

The set-coloring Ramsey number is defined to be the minimum such that if each edge of the complete graph is assigned a set of colors from , then one of the colors contains a monochromatic clique of size . The case is the usual -color Ramsey number, and the case was studied by Erdős, Hajnal and Rado in 1965, and by Erdős and Szemerédi in 1972. The first significant results for general were obtained only recently, by Conlon, Fox, He, Mubayi, Suk and Verstraëte, who showed that if is bounded away from 0 and 1.

Ubiquity of graphs with nowhere-linear end structure.

A graph is said to be -, where is the minor relation between graphs, if whenever is a graph with for all , then one also has , where is the disjoint union of many copies of . A well-known conjecture of Andreae is that every locally finite connected graph is -ubiquitous. In this paper we give a sufficient condition on the structure of the ends of a graph which implies that is -ubiquitous.

Hamiltonian decompositions of 4-regular Cayley graphs of infinite abelian groups.

A well-known conjecture of Alspach says that every -regular Cayley graph of a finite abelian group can be decomposed into Hamiltonian cycles. We consider an analogous question for infinite abelian groups. In this setting one natural analogue of a Hamiltonian cycle is a spanning double-ray.