{"title":"计算密集超图中的跨越子图","authors":"Richard Montgomery, Matías Pavez-Signé","doi":"10.1017/s0963548324000178","DOIUrl":null,"url":null,"abstract":"We give a simple method to estimate the number of distinct copies of some classes of spanning subgraphs in hypergraphs with a high minimum degree. In particular, for each <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline1.png\"/> <jats:tex-math> $k\\geq 2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> and <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline2.png\"/> <jats:tex-math> $1\\leq \\ell \\leq k-1$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, we show that every <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline3.png\"/> <jats:tex-math> $k$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-graph on <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline4.png\"/> <jats:tex-math> $n$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> vertices with minimum codegree at least<jats:disp-formula> <jats:alternatives> <jats:graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" mimetype=\"image\" position=\"float\" xlink:href=\"S0963548324000178_eqnU1.png\"/> <jats:tex-math> \\begin{equation*} \\left \\{\\begin {array}{l@{\\quad}l} \\left (\\dfrac {1}{2}+o(1)\\right )n & \\text { if }(k-\\ell )\\mid k,\\\\[5pt] \\left (\\dfrac {1}{\\lceil \\frac {k}{k-\\ell }\\rceil (k-\\ell )}+o(1)\\right )n & \\text { if }(k-\\ell )\\nmid k, \\end {array} \\right . \\end{equation*} </jats:tex-math> </jats:alternatives> </jats:disp-formula>contains <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline5.png\"/> <jats:tex-math> $\\exp\\!(n\\log n-\\Theta (n))$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> Hamilton <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline6.png\"/> <jats:tex-math> $\\ell$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-cycles as long as <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline7.png\"/> <jats:tex-math> $(k-\\ell )\\mid n$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. When <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline8.png\"/> <jats:tex-math> $(k-\\ell )\\mid k$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, this gives a simple proof of a result of Glock, Gould, Joos, Kühn, and Osthus, while when <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline9.png\"/> <jats:tex-math> $(k-\\ell )\\nmid k$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, this gives a weaker count than that given by Ferber, Hardiman, and Mond, or when <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S0963548324000178_inline10.png\"/> <jats:tex-math> $\\ell \\lt k/2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, by Ferber, Krivelevich, and Sudakov, but one that holds for an asymptotically optimal minimum codegree bound.","PeriodicalId":10503,"journal":{"name":"Combinatorics, Probability and Computing","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Counting spanning subgraphs in dense hypergraphs\",\"authors\":\"Richard Montgomery, Matías Pavez-Signé\",\"doi\":\"10.1017/s0963548324000178\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"We give a simple method to estimate the number of distinct copies of some classes of spanning subgraphs in hypergraphs with a high minimum degree. In particular, for each <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline1.png\\\"/> <jats:tex-math> $k\\\\geq 2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> and <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline2.png\\\"/> <jats:tex-math> $1\\\\leq \\\\ell \\\\leq k-1$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, we show that every <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline3.png\\\"/> <jats:tex-math> $k$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-graph on <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline4.png\\\"/> <jats:tex-math> $n$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> vertices with minimum codegree at least<jats:disp-formula> <jats:alternatives> <jats:graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" mimetype=\\\"image\\\" position=\\\"float\\\" xlink:href=\\\"S0963548324000178_eqnU1.png\\\"/> <jats:tex-math> \\\\begin{equation*} \\\\left \\\\{\\\\begin {array}{l@{\\\\quad}l} \\\\left (\\\\dfrac {1}{2}+o(1)\\\\right )n & \\\\text { if }(k-\\\\ell )\\\\mid k,\\\\\\\\[5pt] \\\\left (\\\\dfrac {1}{\\\\lceil \\\\frac {k}{k-\\\\ell }\\\\rceil (k-\\\\ell )}+o(1)\\\\right )n & \\\\text { if }(k-\\\\ell )\\\\nmid k, \\\\end {array} \\\\right . \\\\end{equation*} </jats:tex-math> </jats:alternatives> </jats:disp-formula>contains <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline5.png\\\"/> <jats:tex-math> $\\\\exp\\\\!(n\\\\log n-\\\\Theta (n))$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> Hamilton <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline6.png\\\"/> <jats:tex-math> $\\\\ell$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>-cycles as long as <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline7.png\\\"/> <jats:tex-math> $(k-\\\\ell )\\\\mid n$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. When <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline8.png\\\"/> <jats:tex-math> $(k-\\\\ell )\\\\mid k$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, this gives a simple proof of a result of Glock, Gould, Joos, Kühn, and Osthus, while when <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline9.png\\\"/> <jats:tex-math> $(k-\\\\ell )\\\\nmid k$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, this gives a weaker count than that given by Ferber, Hardiman, and Mond, or when <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\\\"http://www.w3.org/1999/xlink\\\" mime-subtype=\\\"png\\\" xlink:href=\\\"S0963548324000178_inline10.png\\\"/> <jats:tex-math> $\\\\ell \\\\lt k/2$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>, by Ferber, Krivelevich, and Sudakov, but one that holds for an asymptotically optimal minimum codegree bound.\",\"PeriodicalId\":10503,\"journal\":{\"name\":\"Combinatorics, Probability and Computing\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2024-05-30\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Combinatorics, Probability and Computing\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.1017/s0963548324000178\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Combinatorics, Probability and Computing","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1017/s0963548324000178","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
We give a simple method to estimate the number of distinct copies of some classes of spanning subgraphs in hypergraphs with a high minimum degree. In particular, for each $k\geq 2$ and $1\leq \ell \leq k-1$ , we show that every $k$ -graph on $n$ vertices with minimum codegree at least \begin{equation*} \left \{\begin {array}{l@{\quad}l} \left (\dfrac {1}{2}+o(1)\right )n & \text { if }(k-\ell )\mid k,\\[5pt] \left (\dfrac {1}{\lceil \frac {k}{k-\ell }\rceil (k-\ell )}+o(1)\right )n & \text { if }(k-\ell )\nmid k, \end {array} \right . \end{equation*} contains $\exp\!(n\log n-\Theta (n))$ Hamilton $\ell$ -cycles as long as $(k-\ell )\mid n$ . When $(k-\ell )\mid k$ , this gives a simple proof of a result of Glock, Gould, Joos, Kühn, and Osthus, while when $(k-\ell )\nmid k$ , this gives a weaker count than that given by Ferber, Hardiman, and Mond, or when $\ell \lt k/2$ , by Ferber, Krivelevich, and Sudakov, but one that holds for an asymptotically optimal minimum codegree bound.