Graph homomorphisms and chromatic numbers are foundational concepts in modern graph theory, with widespread applications that extend from combinatorial optimisation to theoretical computer science. A ...

A k-graph is an ordered couple (V, E) where V is a set and E a set of k-tuples of elements of V; thus, a 2-graph is an ordinary graph. If the notions of the independent set and the chromatic number ...

In 1950 Edward Nelson, then a student at the University of Chicago, asked the kind of deceptively simple question that can give mathematicians fits for decades. Imagine, he said, a graph — a ...