Sangam: A Confluence of Knowledge Streams

Cayley Graphs Without a Bounded Eigenbasis

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dc.contributor Massachusetts Institute of Technology. Department of Mathematics
dc.creator Sah, Ashwin
dc.creator Sawhney, Mehtaab
dc.creator Zhao, Yufei
dc.date 2022-10-18T16:47:13Z
dc.date 2022-10-18T16:47:13Z
dc.date 2020
dc.date 2022-10-18T16:39:01Z
dc.date.accessioned 2023-03-01T18:08:57Z
dc.date.available 2023-03-01T18:08:57Z
dc.identifier https://hdl.handle.net/1721.1/145890
dc.identifier Sah, Ashwin, Sawhney, Mehtaab and Zhao, Yufei. 2020. "Cayley Graphs Without a Bounded Eigenbasis." International Mathematics Research Notices, 2022 (8).
dc.identifier.uri http://localhost:8080/xmlui/handle/CUHPOERS/278933
dc.description <jats:title>Abstract</jats:title> <jats:p>Does every $n$-vertex Cayley graph have an orthonormal eigenbasis all of whose coordinates are $O(1/\sqrt{n})$? While the answer is yes for abelian groups, we show that it is no in general. On the other hand, we show that every $n$-vertex Cayley graph (and more generally, vertex-transitive graph) has an orthonormal basis whose coordinates are all $O(\sqrt{\log n / n})$, and that this bound is nearly best possible. Our investigation is motivated by a question of Assaf Naor, who proved that random abelian Cayley graphs are small-set expanders, extending a classic result of Alon–Roichman. His proof relies on the existence of a bounded eigenbasis for abelian Cayley graphs, which we now know cannot hold for general groups. On the other hand, we navigate around this obstruction and extend Naor’s result to nonabelian groups.</jats:p>
dc.format application/pdf
dc.language en
dc.publisher Oxford University Press (OUP)
dc.relation 10.1093/IMRN/RNAA298
dc.relation International Mathematics Research Notices
dc.rights Creative Commons Attribution-Noncommercial-Share Alike
dc.rights http://creativecommons.org/licenses/by-nc-sa/4.0/
dc.source arXiv
dc.title Cayley Graphs Without a Bounded Eigenbasis
dc.type Article
dc.type http://purl.org/eprint/type/JournalArticle


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