arXiv:2503.19069math.STcs.IT2025-03被引 6

提出通用方法检测随机图中任意植入子图,揭示其统计与计算极限。

Detecting Arbitrary Planted Subgraphs in Random Graphs

  • 基于子图边数、最大度和子图密度,统一刻画检测阈值。
  • 在稠密、稀疏及临界三类情形下,证明边界紧致且适用于所有已有结构。
  • 发现检测存在突变相变现象,算法成败随边概率急剧切换。

本文研究在 Erdős-Rényi 随机图 𝒢(n, q_n) 中检测任意植入子图 Γ=Γ_n(内部边概率为 p_n)的问题。在稠密情形下,我们精确刻画了信息论与计算阈值,并给出出现计算-统计间隙的条件;关键在于这些阈值仅依赖于 Γ 的边数、最大度和最大子图密度。我们的上下界对任意 p_n 与 q_n 作为 n 函数均成立。进一步分析稀疏情形(q_n = Θ(n^{-α}),p_n−q_n =Θ(q_n),α∈[0,2])与临界情形(p_n=1−o(1),q_n=Θ(n^{-α})),证明现有文献中所有研究过的子图均满足边界紧致。最后,识别出检测发生尖锐相变的条件:算法成功与失败的边界随 q_n 突然跳跃。

原文摘要 · Abstract (English)

The problems of detecting and recovering planted structures/subgraphs in Erdős-Rényi random graphs, have received significant attention over the past three decades, leading to many exciting results and mathematical techniques. However, prior work has largely focused on specific ad hoc planted structures and inferential settings, while a general theory has remained elusive. In this paper, we bridge this gap by investigating the detection of an \emph{arbitrary} planted subgraph $Γ= Γ_n$ in an Erdős-Rényi random graph $\mathcal{G}(n, q_n)$, where the edge probability within $Γ$ is $p_n$. We examine both the statistical and computational aspects of this problem and establish the following results. In the dense regime, where the edge probabilities $p_n$ and $q_n$ are fixed, we tightly characterize the information-theoretic and computational thresholds for detecting $Γ$, and provide conditions under which a computational-statistical gap arises. Most notably, these thresholds depend on $Γ$ only through its number of edges, maximum degree, and maximum subgraph density. Our lower and upper bounds are general and apply to any value of $p_n$ and $q_n$ as functions of $n$. Accordingly, we also analyze the sparse regime where $q_n = Θ(n^{-α})$ and $p_n-q_n =Θ(q_n)$, with $α\in[0,2]$, as well as the critical regime where $p_n=1-o(1)$ and $q_n = Θ(n^{-α})$, both of which have been widely studied, for specific choices of $Γ$. For these regimes, we show that our bounds are tight for all planted subgraphs investigated in the literature thus far\textemdash{}and many more. Finally, we identify conditions under which detection undergoes sharp phase transition, where the boundaries at which algorithms succeed or fail shift abruptly as a function of $q_n$.

图检测随机图相变

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