Quantum isomorphic strongly regular graphs from the E8 root system

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In this article, we give a first example of a pair of quantum isomorphic, non-isomorphic strongly regular graphs, that is, non-isomorphic strongly regular graphs having the same homomorphism counts from all planar graphs. The pair consists of the orthogonality graph of the 120 lines spanned by the E8 root system and a rank 4 graph whose complement was first discovered by Brouwer, Ivanov and Klin. Both graphs are strongly regular with parameters (120, 63, 30, 36). Using Godsil-McKay switching, we obtain more quantum isomorphic, non-isomorphic strongly regular graphs with the same parameters.

Original languageEnglish
JournalAlgebraic Combinatorics
Volume7
Issue number2
Pages (from-to)515-528
Number of pages14
ISSN2589-5486
DOIs
Publication statusPublished - 2024

Bibliographical note

Publisher Copyright:
© The author(s), 2024.

    Research areas

  • Godsil–McKay switching, quantum isomorphism, root systems, strongly regular graphs

ID: 392562112