On the largest strongly connected component of randomly oriented divisor graphs

Fuente: arXiv
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Main Authors: Kim, Jihyung, Phillips, Tristan
Format: Preprint
Published: 2026
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author Kim, Jihyung
Phillips, Tristan
author_facet Kim, Jihyung
Phillips, Tristan
contents We introduce the study of \textit{randomly oriented divisor graphs}. For each $ρ\in [0,1]$, the randomly oriented divisor graph $\mathcal{D}_ρ(N)$ is obtained from the divisor graph on $\{1, 2, \ldots, N\}$ by directing each edge according to divisibility and independently reversing the direction of each edge with probability $ρ$. We study the expected size of the largest strongly connected component, $\textbf{E}[\#Φ(\mathcal{D}_ρ(N))]$. Our main result gives a lower bound for this quantity in terms of the distribution of values of the divisor function $τ(n)$. As a consequence, we show that for any fixed $ρ\in (0,1)$, the largest strongly connected component has expected size asymptotic to $N$. To obtain explicit bounds, we prove an effective version of a theorem of Hardy and Ramanujan on the normal order of $\log τ(n)$, which may be of independent interest.
format Preprint
id arxiv_https___arxiv_org_abs_2604_05176
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the largest strongly connected component of randomly oriented divisor graphs
Kim, Jihyung
Phillips, Tristan
Combinatorics
Number Theory
Primary: 05C80, 11N37, Secondary: 05C20, 11N56, 60C05
We introduce the study of \textit{randomly oriented divisor graphs}. For each $ρ\in [0,1]$, the randomly oriented divisor graph $\mathcal{D}_ρ(N)$ is obtained from the divisor graph on $\{1, 2, \ldots, N\}$ by directing each edge according to divisibility and independently reversing the direction of each edge with probability $ρ$. We study the expected size of the largest strongly connected component, $\textbf{E}[\#Φ(\mathcal{D}_ρ(N))]$. Our main result gives a lower bound for this quantity in terms of the distribution of values of the divisor function $τ(n)$. As a consequence, we show that for any fixed $ρ\in (0,1)$, the largest strongly connected component has expected size asymptotic to $N$. To obtain explicit bounds, we prove an effective version of a theorem of Hardy and Ramanujan on the normal order of $\log τ(n)$, which may be of independent interest.
title On the largest strongly connected component of randomly oriented divisor graphs
topic Combinatorics
Number Theory
Primary: 05C80, 11N37, Secondary: 05C20, 11N56, 60C05
url https://arxiv.org/abs/2604.05176