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Hamiltonicity of sparse pseudorandom graphs

Published online by Cambridge University Press:  25 March 2025

Asaf Ferber
Affiliation:
Department of Mathematics, University of California, Irvine, CA, USA
Jie Han
Affiliation:
School of Mathematics and Statistics and Center for Applied Mathematics, Beijing Institute of Technology, Beijing, China
Dingjia Mao*
Affiliation:
Department of Mathematics, University of California, Irvine, CA, USA
Roman Vershynin
Affiliation:
Department of Mathematics, University of California, Irvine, CA, USA
*
Corresponding author: Dingjia Mao; Email: [email protected]

Abstract

We show that every $(n,d,\lambda )$-graph contains a Hamilton cycle for sufficiently large $n$, assuming that $d\geq \log ^{6}n$ and $\lambda \leq cd$, where $c=\frac {1}{70000}$. This significantly improves a recent result of Glock, Correia, and Sudakov, who obtained a similar result for $d$ that grows polynomially with $n$. The proof is based on a new result regarding the second largest eigenvalue of the adjacency matrix of a subgraph induced by a random subset of vertices, combined with a recent result on connecting designated pairs of vertices by vertex-disjoint paths in $(n,d,\lambda )$-graphs. We believe that the former result is of independent interest and will have further applications.

Type
Paper
Copyright
© The Author(s), 2025. Published by Cambridge University Press

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