Some problems on induced subgraphs

Abstract

We discuss some problems related to induced subgraphs. The first problem is about getting a good upper bound for the chromatic number in terms of the clique number for graphs in which every induced cycle has length $3$ or $4$. The second problem is about the perfect chromatic number of a graph, which is the smallest number of perfect sets into which the vertex set of a graph can be partitioned. (A set of vertices is said to be perfect it it induces a perfect graph.) The third problem is on antichains in the induced subgraph ordering. The fourth problem is on graphs in which the difference between the chromatic number and the clique number is at most one for every induced subgraph of the graph. The fifth problem is on a weakening of the notorious Erd\H{o}s-Hajnal conjecture. The last problem is on a conjecture of Gy\'{a}rf\'{a}s about $\chi$-boundedness of a particular class of graphs.