A construction of cospectral graphs for the normalized Laplacian
The electronic journal of combinatorics, Tome 18 (2011) no. 1
We give a method to construct cospectral graphs for the normalized Laplacian by a local modification in some graphs with special structure. Namely, under some simple assumptions, we can replace a small bipartite graph with a cospectral mate without changing the spectrum of the entire graph. We also consider a related result for swapping out biregular bipartite graphs for the matrix $A+tD$. We produce (exponentially) large families of non-bipartite, non-regular graphs which are mutually cospectral, and also give an example of a graph which is cospectral with its complement but is not self-complementary.
DOI :
10.37236/718
Classification :
05C50
Mots-clés : normalized Laplacian, cospectral, bipartite subgraph swapping
Mots-clés : normalized Laplacian, cospectral, bipartite subgraph swapping
@article{10_37236_718,
author = {Steve Butler and Jason Grout},
title = {A construction of cospectral graphs for the normalized {Laplacian}},
journal = {The electronic journal of combinatorics},
year = {2011},
volume = {18},
number = {1},
doi = {10.37236/718},
zbl = {1243.05144},
url = {http://geodesic.mathdoc.fr/articles/10.37236/718/}
}
Steve Butler; Jason Grout. A construction of cospectral graphs for the normalized Laplacian. The electronic journal of combinatorics, Tome 18 (2011) no. 1. doi: 10.37236/718
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