Jump to ContentJump to Main Navigation
Graphs and Homomorphisms$
Users without a subscription are not able to see the full content.

Pavol Hell and Jaroslav Nesetril

Print publication date: 2004

Print ISBN-13: 9780198528173

Published to Oxford Scholarship Online: September 2007

DOI: 10.1093/acprof:oso/9780198528173.001.0001

Show Summary Details
Page of

PRINTED FROM OXFORD SCHOLARSHIP ONLINE (www.oxfordscholarship.com). (c) Copyright Oxford University Press, 2019. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 14 October 2019

THE STRUCTURE OF COMPOSITION

THE STRUCTURE OF COMPOSITION

Chapter:
(p.109) 4 THE STRUCTURE OF COMPOSITION
Source:
Graphs and Homomorphisms
Author(s):

Pavol Hell

Jaroslav Nešetřil

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780198528173.003.0004

This chapter focuses on the structure, as opposed to just the existence, of the family of homomorphisms among a set of graphs. The difference is noticeable with even just one graph. For instance, a graph having only the identity homomorphisms to itself is called rigid; rigid graphs are the building blocks of many constructions. Many useful constructions of rigid graphs are provided, and it is shown that asymptotically almost all graphs are rigid; infinite rigid graphs with arbitrary cardinality are also constructed. The homomorphisms among a set of graphs impose the algebraic structure of a category, and every finite category is represented by a set of graphs. This is the generalization of the theorem of Frucht from Chapter 1. Also, as in the case studied by Frucht, it is shown that the representing graphs can be required to have any of a number of graph theoretic properties. However, these properties cannot include having bounded degrees — somewhat surprisingly, since Frucht proved that cubic graphs represent all finite groups.

Keywords:   homomorphism composition, rigid graph, infinite graphs, category, graphs, endomorphism monoid, automorphism group, Isbell’s Condition

Oxford Scholarship Online requires a subscription or purchase to access the full text of books within the service. Public users can however freely search the site and view the abstracts and keywords for each book and chapter.

Please, subscribe or login to access full text content.

If you think you should have access to this title, please contact your librarian.

To troubleshoot, please check our FAQs , and if you can't find the answer there, please contact us .