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Learning Stable Digraphs from Sparse-Input Linear Structural Causal Models
Proceedings of the 42nd Conference on Uncertainty in Artificial Intelligence, PMLR 337:4561-4594, 2026.
Abstract
We propose StableSpIn, a continuous optimization framework for learning potentially cyclic causal directed graphs (digraphs) in linear structural equation models via a spectral-radius constraint on the absolute adjacency matrix. Our motivation is twofold: first, stability is a natural requirement for linear structural models; second, the contractive cycles that stability induces facilitate the identifiability of digraphs. We formulate causal discovery as a likelihood-based optimization problem under a sparse-input assumption, yielding a scalable algorithm applicable to both cross-sectional and time-series data. Unlike prior continuous acyclicity constraints, our stability regularizer is cheaper to evaluate while accommodating general digraphs, yielding faster optimization in practice. Experiments on synthetic benchmarks show improved graph recovery over state-of-the-art baselines, and empirical studies on U.S., European, and Swiss equity markets reveal interpretable cyclic dependencies that persist across time windows. Our implementation is available at https://github.com/pmisiakos/StableSpIn.