Eigenvectors of the De Bruijn Graph Laplacian: A Natural Basis for the Cut and Cycle Space

Fuente: arXiv
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Autori principali: Philippakis, Anthony, Mallinar, Neil, Pandit, Parthe, Belkin, Mikhail
Natura: Preprint
Pubblicazione: 2024
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author Philippakis, Anthony
Mallinar, Neil
Pandit, Parthe
Belkin, Mikhail
author_facet Philippakis, Anthony
Mallinar, Neil
Pandit, Parthe
Belkin, Mikhail
contents We study the Laplacian of the undirected De Bruijn graph over an alphabet $A$ of order $k$. While the eigenvalues of this Laplacian were found in 1998 by Delorme and Tillich [1], an explicit description of its eigenvectors has remained elusive. In this work, we find these eigenvectors in closed form and show that they yield a natural and canonical basis for the cut- and cycle-spaces of De Bruijn graphs. Remarkably, we find that the cycle basis we construct is a basis for the cycle space of both the undirected and the directed De Bruijn graph. This is done by developing an analogue of the Fourier transform on the De Bruijn graph, which acts to diagonalize the Laplacian. Moreover, we show that the cycle-space of De Bruijn graphs, when considering all possible orders of $k$ simultaneously, contains a rich algebraic structure, that of a graded Hopf algebra.
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id arxiv_https___arxiv_org_abs_2410_07622
institution arXiv
publishDate 2024
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spellingShingle Eigenvectors of the De Bruijn Graph Laplacian: A Natural Basis for the Cut and Cycle Space
Philippakis, Anthony
Mallinar, Neil
Pandit, Parthe
Belkin, Mikhail
Combinatorics
Rings and Algebras
We study the Laplacian of the undirected De Bruijn graph over an alphabet $A$ of order $k$. While the eigenvalues of this Laplacian were found in 1998 by Delorme and Tillich [1], an explicit description of its eigenvectors has remained elusive. In this work, we find these eigenvectors in closed form and show that they yield a natural and canonical basis for the cut- and cycle-spaces of De Bruijn graphs. Remarkably, we find that the cycle basis we construct is a basis for the cycle space of both the undirected and the directed De Bruijn graph. This is done by developing an analogue of the Fourier transform on the De Bruijn graph, which acts to diagonalize the Laplacian. Moreover, we show that the cycle-space of De Bruijn graphs, when considering all possible orders of $k$ simultaneously, contains a rich algebraic structure, that of a graded Hopf algebra.
title Eigenvectors of the De Bruijn Graph Laplacian: A Natural Basis for the Cut and Cycle Space
topic Combinatorics
Rings and Algebras
url https://arxiv.org/abs/2410.07622