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There is no going back: Properties of the non-backtracking Laplacian

  • Raffaella Mulas*
  • , Dong Zhang
  • , Giulio Zucal
  • *Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

We prove new properties of the non-backtracking graph and the non-backtracking Laplacian for graphs. In particular, among other results, we prove that two simple graphs are isomorphic if and only if their corresponding non-backtracking graphs are isomorphic, and we investigate properties of various classes of non-backtracking Laplacian eigenfunctions, such as symmetric and antisymmetric eigenfunctions. Moreover, we introduce and study circularly partite graphs as a generalization of bipartite graphs, and we use this notion to state a sharp upper bound for the spectral gap from 1. We also investigate the singular values of the non-backtracking Laplacian in relation to independence numbers, and we use them to bound the moduli of the eigenvalues.

Original languageEnglish
Pages (from-to)341-370
Number of pages30
JournalLinear Algebra and its Applications
Volume680
Early online date20 Oct 2023
DOIs
Publication statusPublished - 1 Jan 2024

Bibliographical note

Funding Information:
In 2022, Raffaella Mulas and Leo Torres gave a course on non-backtracking operators of graphs at the Max Planck Institute for Mathematics in the Sciences. As part of the course material, and as a follow-up to their first joint article, they prepared a list of open questions on the non-backtracking Laplacian that led to many discussions and exchanging of ideas with some of the course attendees, and eventually to this paper. As such, we would particularly like to express our gratitude to Leo Torres for his indirect contribution to this work. We would also like to thank Florentin Münch, Jiaxi Nie and, in particular, Janis Keck for the helpful comments and interesting discussions. Last (and least), we are grateful to Conor Finn for helping us choosing a suggestive title which we hope will not be rejected.

Publisher Copyright:
© 2023 The Author(s)

Funding

In 2022, Raffaella Mulas and Leo Torres gave a course on non-backtracking operators of graphs at the Max Planck Institute for Mathematics in the Sciences. As part of the course material, and as a follow-up to their first joint article, they prepared a list of open questions on the non-backtracking Laplacian that led to many discussions and exchanging of ideas with some of the course attendees, and eventually to this paper. As such, we would particularly like to express our gratitude to Leo Torres for his indirect contribution to this work. We would also like to thank Florentin Münch, Jiaxi Nie and, in particular, Janis Keck for the helpful comments and interesting discussions. Last (and least), we are grateful to Conor Finn for helping us choosing a suggestive title which we hope will not be rejected.

Keywords

  • Eigenfunctions
  • Eigenvalues
  • Non-backtracking graph
  • Non-backtracking Laplacian
  • Singular values

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