{"status":"public","_id":"17376","author":[{"full_name":"Kwan, Matthew Alan","id":"5fca0887-a1db-11eb-95d1-ca9d5e0453b3","last_name":"Kwan","first_name":"Matthew Alan","orcid":"0000-0002-4003-7567"},{"last_name":"Wigderson","first_name":"Yuval","full_name":"Wigderson, Yuval"}],"article_type":"original","quality_controlled":"1","title":"The inertia bound is far from tight","main_file_link":[{"open_access":"1","url":"https://doi.org/10.1112/blms.13127"}],"oa_version":"Published Version","project":[{"grant_number":"101076777","_id":"bd95085b-d553-11ed-ba76-e55d3349be45","name":"Randomness and structure in combinatorics"}],"day":"30","citation":{"chicago":"Kwan, Matthew Alan, and Yuval Wigderson. “The Inertia Bound Is Far from Tight.” <i>Bulletin of the London Mathematical Society</i>. London Mathematical Society, 2024. <a href=\"https://doi.org/10.1112/blms.13127\">https://doi.org/10.1112/blms.13127</a>.","ista":"Kwan MA, Wigderson Y. 2024. The inertia bound is far from tight. Bulletin of the London Mathematical Society.","apa":"Kwan, M. A., &#38; Wigderson, Y. (2024). The inertia bound is far from tight. <i>Bulletin of the London Mathematical Society</i>. London Mathematical Society. <a href=\"https://doi.org/10.1112/blms.13127\">https://doi.org/10.1112/blms.13127</a>","ama":"Kwan MA, Wigderson Y. The inertia bound is far from tight. <i>Bulletin of the London Mathematical Society</i>. 2024. doi:<a href=\"https://doi.org/10.1112/blms.13127\">10.1112/blms.13127</a>","mla":"Kwan, Matthew Alan, and Yuval Wigderson. “The Inertia Bound Is Far from Tight.” <i>Bulletin of the London Mathematical Society</i>, London Mathematical Society, 2024, doi:<a href=\"https://doi.org/10.1112/blms.13127\">10.1112/blms.13127</a>.","short":"M.A. Kwan, Y. Wigderson, Bulletin of the London Mathematical Society (2024).","ieee":"M. A. Kwan and Y. Wigderson, “The inertia bound is far from tight,” <i>Bulletin of the London Mathematical Society</i>. London Mathematical Society, 2024."},"date_updated":"2024-08-05T07:13:18Z","department":[{"_id":"MaKw"}],"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","scopus_import":"1","month":"07","publication_identifier":{"issn":["0024-6093"],"eissn":["1469-2120"]},"external_id":{"arxiv":["2312.04925"]},"oa":1,"publisher":"London Mathematical Society","type":"journal_article","doi":"10.1112/blms.13127","date_created":"2024-08-04T22:01:22Z","language":[{"iso":"eng"}],"publication":"Bulletin of the London Mathematical Society","date_published":"2024-07-30T00:00:00Z","article_processing_charge":"Yes (via OA deal)","acknowledgement":"The authors are grateful to Noga Alon, Anurag Bishnoi, Clive Elphick, and Ferdinand Ihringer for helpful comments and interesting discussions on earlier drafts of this paper. Matthew Kwan is supported by ERC Starting Grant “RANDSTRUCT” No. 101076777. Yuval Wigderson is supported by Dr. Max Rössler, the Walter Haefner Foundation, and the ETH Zürich Foundation.\r\nOpen access funding provided by Eidgenossische Technische Hochschule Zurich.","abstract":[{"lang":"eng","text":"The inertia bound and ratio bound (also known as the Cvetković bound and Hoffman bound) are two fundamental inequalities in spectral graph theory, giving upper bounds on the independence number α(G) of a graph G in terms of spectral information about a weighted adjacency matrix of G. For both inequalities, given a graph G, one needs to make a judicious choice of weighted adjacency matrix to obtain as strong a bound as possible.\r\nWhile there is a well-established theory surrounding the ratio bound, the inertia bound is much more mysterious, and its limits are rather unclear. In fact, only recently did Sinkovic find the first example of a graph for which the inertia bound is not tight (for any weighted adjacency matrix), answering a longstanding question of Godsil. We show that the inertia bound can be extremely far from tight, and in fact can significantly underperform the ratio bound: for example, one of our results is that for infinitely many n, there is an n-vertex graph for which even the unweighted ratio bound can prove α(G)≤4n3/4, but the inertia bound is always at least n/4. In particular, these results address questions of Rooney, Sinkovic, and Wocjan--Elphick--Abiad."}],"publication_status":"epub_ahead","year":"2024"}