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| Autores principales: | , |
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| Formato: | Preprint |
| Publicado: |
2026
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| Materias: | |
| Acceso en línea: | https://arxiv.org/abs/2605.29553 |
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- We determine the sharp threshold for Hamilton cycles in randomly perturbed sparse graphs. For any $α=α(n)=o(1)$, let $G_α$ be an $n$-vertex graph with minimum degree $δ(G_α)\geαn$. We prove that if $$p\ge(1+\varepsilon)\frac{\log(1/α)}{n},$$ then the union $G_α\cup G(n,p)$ is Hamiltonian asymptotically almost surely. This significantly strengthens a recent result of Hahn-Klimroth, Maesaka, Mogge, Mohr, and Parczyk by improving the leading constant from 6 to the optimal value of 1. Crucially, we show that this bound on $p$ is best possible when $αn\rightarrow\infty$, thereby establishing the exact probability threshold for Hamiltonicity in this sparse regime. Our proof relies on a robust random expansion lemma, Pósa's booster lemma, and a sprinkling argument.