Counting Hamilton Cycles in Dirac Hypergraphs

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Authors
Ferber, Asaf 
Hardiman, Liam 
Mond, Adva 
Abstract

jats:titleAbstract</jats:title>jats:pFor jats:inline-formulajats:alternativesjats:tex-math$$0\le \ell <k$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:mn0</mml:mn> mml:mo≤</mml:mo> mml:miℓ</mml:mi> mml:mo<</mml:mo> mml:mik</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, a Hamilton jats:inline-formulajats:alternativesjats:tex-math$$\ell $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:miℓ</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>-cycle in a jats:italick</jats:italic>-uniform hypergraph jats:italicH</jats:italic> is a cyclic ordering of the vertices of jats:italicH</jats:italic> in which the edges are segments of length jats:italick</jats:italic> and every two consecutive edges overlap in exactly jats:inline-formulajats:alternativesjats:tex-math$$\ell $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:miℓ</mml:mi> </mml:math></jats:alternatives></jats:inline-formula> vertices. We show that for all jats:inline-formulajats:alternativesjats:tex-math$$0\le \ell <k-1$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:mn0</mml:mn> mml:mo≤</mml:mo> mml:miℓ</mml:mi> mml:mo<</mml:mo> mml:mik</mml:mi> mml:mo-</mml:mo> mml:mn1</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, every jats:italick</jats:italic>-graph with minimum co-degree jats:inline-formulajats:alternativesjats:tex-math$$\delta n$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miδ</mml:mi> mml:min</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> with jats:inline-formulajats:alternativesjats:tex-math$$\delta >1/2$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miδ</mml:mi> mml:mo></mml:mo> mml:mn1</mml:mn> mml:mo/</mml:mo> mml:mn2</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> has (asymptotically and up to a subexponential factor) at least as many Hamilton jats:inline-formulajats:alternativesjats:tex-math$$\ell $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:miℓ</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>-cycles as a typical random jats:italick</jats:italic>-graph with edge-probability jats:inline-formulajats:alternativesjats:tex-math$$\delta $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:miδ</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>. This significantly improves a recent result of Glock, Gould, Joos, Kühn and Osthus, and verifies a conjecture of Ferber, Krivelevich and Sudakov for all values jats:inline-formulajats:alternativesjats:tex-math$$0\le \ell <k-1$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:mn0</mml:mn> mml:mo≤</mml:mo> mml:miℓ</mml:mi> mml:mo<</mml:mo> mml:mik</mml:mi> mml:mo-</mml:mo> mml:mn1</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>.</jats:p>

Description

Acknowledgements: The authors are thankful to the anonymous referees for their valuable comments. The first author would like to thank Lisa Sauermann for sharing the observation that was discussed in the concluding remarks section. The third author is thankful to Trinity College of the University of Cambridge for the Trinity Internal Graduate Studentship funding.

Keywords
4901 Applied Mathematics, 4904 Pure Mathematics, 49 Mathematical Sciences
Journal Title
Combinatorica
Conference Name
Journal ISSN
0209-9683
1439-6912
Volume Title
43
Publisher
Springer Science and Business Media LLC