Minimal circular-imperfect graphs of large clique number and large independence number

Minimal circular-imperfect graphs of large clique number and large independence number

This paper constructs some classes of minimal circular-imperfect graphs. In particular, it is proved that there are minimal circularimperfect graphs whose independence number and clique number are both arbitrarily large.

Fractional chromatic number and circular chromatic number for distance graphs with large clique size

Let Z be the set of all integers and M a set of positive integers. The distance graph G(Z,M) generated by M is the graph with vertex set Z and in which i and j are adjacent whenever |i − j| ∈ M . Supported in part by the National Science Foundation under grant DMS 9805945. Supported in part by the National Science Council, R. O. C., under grant NSC892115-M-110-012.

Searching Graphs with Large Clique Number

Independence number and clique minors

Since χ(G) · α(G) ≥ |V (G)|, Hadwiger’s Conjecture implies that any graph G has the complete graph Kdn α e as a minor, where n is the number of vertices of G and α is the maximum number of independent vertices in G. Motivated by this fact, it is shown that any graph on n vertices with independence number α ≥ 3 has the complete graph Kd n 2α−2 e as a minor. This improves the well-known theorem o...

The Independence Number of Graphs with Large Odd Girth

Let G be an r-regular graph of order n and independence number α(G). We show that if G has odd girth 2k + 3 then α(G) ≥ n1−1/kr1/k . We also prove similar results for graphs which are not regular. Using these results we improve on the lower bound of Monien and Speckenmeyer, for the independence number of a graph of order n and odd girth 2k + 3. AMS Subject Classification. 05C15 §