Title
On the Density of Trigraph Homomorphisms
Abstract
An order is dense if A < B implies A < C < B for some C. The homomorphism order of (nontrivial) graphs is known to be dense. Homomorphisms of trigraphs extend homomorphisms of graphs, and model many partitions of interest in the study of perfect graphs. We address the question of density of the homomorphism order for trigraphs. It turns out that there are gaps in the order, and we exactly characterize where they occur.
Year
DOI
Venue
2007
10.1007/s00373-007-0712-5
Graphs and Combinatorics
Keywords
DocType
Volume
homomorphisms,trigraph homomorphisms,gaps,gaps.,homomorphism order,perfect graph,density,trigraphs
Journal
23
Issue
ISSN
Citations 
1
1435-5914
0
PageRank 
References 
Authors
0.34
6
2
Name
Order
Citations
PageRank
Pavol Hell12638288.75
Jarik Nešetřil2323.35