# Statistical limits of correlation detection in trees

arXiv: https://arxiv.org/abs/2209.13723 · HTML: https://mlsanity.com/paper/2209.13723/

## Key facts

- Cited by 12 papers in the map (data through 14 Oct 2026).
- Builds on 15 of its 26 references that are in the map.
- First posted on arXiv 27 Sep 2022.

## Builds on (most cited first, 15 of 15)

- [Notes on Computational Hardness of Hypothesis Testing: Predictions using the Low-Degree Likelihood Ratio](https://mlsanity.com/paper/1907.11636/) (2019)
- [Settling the Sharp Reconstruction Thresholds of Random Graph Matching](https://mlsanity.com/paper/2102.00082/) (2021)
- [Exact alignment recovery for correlated ErdHos-R'enyi graphs](https://mlsanity.com/paper/1711.06783/) (2017)
- [(Nearly) Efficient Algorithms for the Graph Matching Problem on Correlated Random Graphs](https://mlsanity.com/paper/1805.02349/) (2018)
- [Spectral Graph Matching and Regularized Quadratic Relaxations II: ErdHos-R'enyi Graphs and Universality](https://mlsanity.com/paper/1907.08883/) (2019)
- [Partial Recovery in the Graph Alignment Problem](https://mlsanity.com/paper/2007.00533/) (2020)
- [From tree matching to sparse graph alignment](https://mlsanity.com/paper/2002.01258/) (2020)
- [Testing correlation of unlabeled random graphs](https://mlsanity.com/paper/2008.10097/) (2020)
- [Partial Recovery of ErdHos-R'enyi Graph Alignment via k-Core Alignment](https://mlsanity.com/paper/1809.03553/) (2018)
- [Random graph matching at Otter's threshold via counting chandeliers](https://mlsanity.com/paper/2209.12313/) (2022)
- [Testing network correlation efficiently via counting trees](https://mlsanity.com/paper/2110.11816/) (2021)
- [Impossibility of Partial Recovery in the Graph Alignment Problem](https://mlsanity.com/paper/2102.02685/) (2021)
- [Matching recovery threshold for correlated random graphs](https://mlsanity.com/paper/2205.14650/) (2022)
- [Correlation detection in trees for planted graph alignment](https://mlsanity.com/paper/2107.07623/) (2021)
- [Detection threshold for correlated ErdHos-R'enyi graphs via densest subgraphs](https://mlsanity.com/paper/2203.14573/) (2022)

## Built on by (most cited first, 12 of 12)

- [A polynomial-time iterative algorithm for random graph matching with non-vanishing correlation](https://mlsanity.com/paper/2306.00266/) (2023)
- [A polynomial time iterative algorithm for matching Gaussian matrices with non-vanishing correlation](https://mlsanity.com/paper/2212.13677/) (2022)
- [The Umeyama algorithm for matching correlated Gaussian geometric models in the low-dimensional regime](https://mlsanity.com/paper/2402.15095/) (2024)
- [A computational transition for detecting correlated stochastic block models by low-degree polynomials](https://mlsanity.com/paper/2409.00966/) (2024)
- [Efficiently matching random inhomogeneous graphs via degree profiles](https://mlsanity.com/paper/2310.10441/) (2023)
- [Graph Matching via convex relaxation to the simplex](https://mlsanity.com/paper/2310.20609/) (2023)
- [Computational Lower Bounds for Correlated Random Graphs via Algorithmic Contiguity](https://mlsanity.com/paper/2502.09832/) (2025)
- [The feasibility of multi-graph alignment: a Bayesian approach](https://mlsanity.com/paper/2502.17142/) (2025)
- [Testing Dependency of Weighted Random Graphs](https://mlsanity.com/paper/2409.14870/) (2024)
- [Robust Random Graph Matching in Dense Graphs via an Approximate Message Passing Type Algorithm](https://mlsanity.com/paper/2412.16457/) (2024)
- [Chaining 2-FWL GNNs for Combinatorial Graph Alignment](https://mlsanity.com/paper/2510.03086/) (2025)
- [Statistical-computational gap in multiple Gaussian graph alignment](https://mlsanity.com/paper/2512.00610/) (2025)

## Abstract (arXiv)

In this paper we address the problem of testing whether two observed trees (t,t') are sampled either independently or from a joint distribution under which they are correlated. This problem, which we refer to as correlation detection in trees, plays a key role in the study of graph alignment for two correlated random graphs. Motivated by graph alignment, we investigate the conditions of existence of one-sided tests, i.e. tests which have vanishing type I error and non-vanishing power in the limit of large tree depth. For the correlated Galton-Watson model with Poisson offspring of mean λ>0 and correlation parameter s ∈ (0,1), we identify a phase transition in the limit of large degrees at s = √α, where α ~ 0.3383 is Otter's constant. Namely, we prove that no such test exists for s ≤ √α, and that such a test exists whenever s > √α, for λ large enough. This result sheds new light on the graph alignment problem in the sparse regime (with O(1) average node degrees) and on the performance of the MPAlign method studied in Ganassali et al. (2021), Piccioli et al. (2021), proving in particular the conjecture of Piccioli et al. (2021) that MPAlign succeeds in the partial recovery task for correlation parameter s>√α provided the average node degree λ is large enough. As a byproduct, we identify a new family of orthogonal polynomials for the Poisson-Galton-Watson measure which enjoy remarkable properties. These polynomials may be of independent interest for a variety of problems involving graphs, trees or branching processes, beyond the scope of graph alignment.