Given a bipartite connected finite graph G=(V, E) and a vertex v 0 # V, we consider a uniform probability measure on the set of graph homomorphisms f : V Γ Z satisfying f (v 0 )=0. This measure can be viewed as a G-indexed random walk on Z, generalizing both the usual time-indexed random walk and tr
Graph homomorphisms through random walks
β Scribed by Amir Daneshgar; Hossein Hajiabolhassan
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 174 KB
- Volume
- 44
- Category
- Article
- ISSN
- 0364-9024
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β¦ Synopsis
Abstract
In this paper we introduce some general necessary conditions for the existence of graph homomorphisms, which hold in both directed and undirected cases. Our method is a combination of Diaconis and SaloffβCoste comparison technique for Markov chains and a generalization of Haemers interlacing theorem. As some applications, we obtain a necessary condition for the spanning subgraph problem, which also provides a generalization of a theorem of Mohar (1992) as a necessary condition for Hamiltonicity. In particular, in the case that the range is a Cayley graph or an edgeβtransitive graph, we obtain theorems with a corollary about the existence of homomorphisms to cycles. This, specially, provides a proof of the fact that the Coxeter graph is a core. Also, we obtain some information about the cores of vertexβtransitive graphs. Β© 2003 Wiley Periodicals, Inc. J Graph Theory 44: 15β38, 2003
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