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arXiv · 1404.4342

Connectedness and isomorphism properties of the zig-zag product of graphs

Daniele D'Angeli·Alfredo Donno·Ecaterina Sava-Huss
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Abstract

In this paper we investigate the connectedness and the isomorphism problems for zig-zag products of two graphs. A sufficient condition for the zig-zag product of two graphs to be connected is provided, reducing to the study of the connectedness property of a new graph which depends only on the second factor of the graph product. We show that, when the second factor is a cycle graph, the study of the isomorphism problem for the zig-zag product is equivalent to the study of the same problem for the associated pseudo-replacement graph. The latter is defined in a natural way, by a construction generalizing the classical replacement product, and its degree is smaller than the degree of the zig-zag product graph. Two particular classes of products are studied in detail: the zig-zag product of a complete graph with a cycle graph, and the zig-zag product of a $4$-regular graph with the cycle graph of length $4$. Furthermore, an example coming from the theory of Schreier graphs associated with the action of self-similar groups is also considered: the graph products are completely determined and their spectral analysis is developed.

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Daniele D'Angeli, Alfredo Donno, Ecaterina Sava-Huss. 2014-04-16. Connectedness and isomorphism properties of the zig-zag product of graphs. https://doi.org/10.1002/jgt.21917

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