{ "id": "2102.11104", "version": "v1", "published": "2021-02-22T15:25:23.000Z", "updated": "2021-02-22T15:25:23.000Z", "title": "Minimum degree stability of $H$-free graphs", "authors": [ "Freddie Illingworth" ], "comment": "12 pages, 2 figures", "categories": [ "math.CO" ], "abstract": "Given an $(r + 1)$-chromatic graph $H$, the fundamental edge stability result of Erd\\H{o}s and Simonovits says that all $n$-vertex $H$-free graphs have at most $(1 - 1/r + o(1)) \\binom{n}{2}$ edges, and any $H$-free graph with that many edges can be made $r$-partite by deleting $o(n^{2})$ edges. Here we consider a natural variant of this -- the minimum degree stability of $H$-free graphs. In particular, what is the least $c$ such that any $n$-vertex $H$-free graph with minimum degree greater than $cn$ can be made $r$-partite by deleting $o(n^{2})$ edges? We determine this least value for all 3-chromatic $H$ and for very many non-3-colourable $H$ (all those in which one is commonly interested) as well as bounding it for the remainder. This extends the Andr\\'{a}sfai-Erd\\H{o}s-S\\'{o}s theorem and work of Alon and Sudakov.", "revisions": [ { "version": "v1", "updated": "2021-02-22T15:25:23.000Z" } ], "analyses": { "subjects": [ "05C35" ], "keywords": [ "free graph", "minimum degree stability", "fundamental edge stability result", "minimum degree greater", "chromatic graph" ], "note": { "typesetting": "TeX", "pages": 12, "language": "en", "license": "arXiv", "status": "editable" } } }