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Detection-Recovery Gap for Planted Dense Cycles
Proceedings of Thirty Sixth Conference on Learning Theory, PMLR 195:2440-2481, 2023.
Abstract
Planted dense cycles are a type of latent structure that appears in many applications, such as small-world networks in social sciences and sequence assembly in computational biology. We consider a model where a dense cycle with expected bandwidth nτ and edge density p is planted in an Erdős–Rényi graph G(n,q). We characterize the computational thresholds for the associated detection and recovery problems for the class of low-degree polynomial algorithms. In particular, a gap exists between the two thresholds in a certain regime of parameters. For example, if n−3/4≪τ≪n−1/2 and p=Cq=Θ(1) for a constant C>1, the detection problem is computationally easy while the recovery problem is hard for low-degree algorithms.