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Counting spanning subgraphs in dense hypergraphs

Published online by Cambridge University Press:  30 May 2024

Richard Montgomery
Affiliation:
Mathematics Institute, Zeeman Building, University of Warwick, Coventry, UK
Matías Pavez-Signé*
Affiliation:
Center for Mathematical Modeling (CNRS IRL2807), University of Chile, Santiago, Chile
*
Corresponding author: Matías Pavez-Signé; Email: [email protected]

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 $k\geq 2$ 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.

Type
Paper
Copyright
© The Author(s), 2024. Published by Cambridge University Press

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