A graph with nodes 1. \_.., n is a threshold signed graph if one can find two positive real numbers S,T and real numbers a , , ..., a, associated with the vertices in such a way that i,j are linked iff either la, + a,/ 3 S or la, -ail T. Such graphs generalize threshold graphs. It is shown that thes
Characterization of graphs with hall number 2
✍ Scribed by Changiz Eslahchi; Matthew Johnson
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 165 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0364-9024
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✦ Synopsis
Abstract
Hall's condition is a simple requirement that a graph G and list assignment L must satisfy if G is to have a proper L‐colouring. The Hall number of G is the smallest integer m such that whenever the lists on the vertices each has size at least m and Hall's condition is satisfied a proper L‐colouring exists. Hilton and P.D. Johnson introduced the parameter and showed that a graph has Hall number 1 if and only if every block is a clique. In this paper we give a forbidden‐induced‐subgraph characterization of graphs with Hall number 2. © 2003 Wiley Periodicals, Inc. J Graph Theory 45: 81–100, 2004
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