## Abstract We prove that the multiplicity of the root 1 in the chromatic polynomial of a simple graph __G__ is equal to the number of nontrivial blocks in __G__. In particular, a connected simple graph __G__ has a cutpoint if and only if its chromatic polynomial is divisible by (ฮป โ 1)^2^. We appl
Expansions of the chromatic polynomial
โ Scribed by Norman Biggs
- Publisher
- Elsevier Science
- Year
- 1973
- Tongue
- English
- Weight
- 739 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0012-365X
No coin nor oath required. For personal study only.
โฆ Synopsis
The chromatic polynomial ;X chromial) of a graph was first defined by Birkhoff in 1912, ;md gives the number of ways or" properly colov iing the vertices of the graph with any number of colours. A good survey of the b-sic facts about these polynomials may be found in the article by Read [ 3 3 .
It has recently been noticed that some classical problems of physics can be expressed in terms of chromials, and papers by Nagle 12 1, Baker [ 1 ] , Temperley and Lieb [4], are concerned with methods of expanding the chromial for use in such problems. In this note we shall unify. simplify, and generalise their treatments, confining our attention to the theoretical basis of the methods.
Y(E,3W VIE,) = vr,
W(E,)n V(E2)I=Oor 1.
๐ SIMILAR VOLUMES
It is proved that the chromatic polynomial of a connected graph with n vertices and m edges has a root with modulus at least (m&1)ร(n&2); this bound is best possible for trees and 2-trees (only). It is also proved that the chromatic polynomial of a graph with few triangles that is not a forest has a
Let P(G, \*) denote the chromatic polynomial of a graph G. It is proved in this paper that for every connected graph G of order n and real number \* n, (\*&2) n&1 P(G, \*)&\*(\*&1) n&2 P(G, \*&1) 0. By this result, the following conjecture proposed by Bartels and Welsh is proved: P(G, n)(P(G, n&1))