arXiv Statistics ML By Kamillo Ferry, Anthea Monod, Keisuke Yano

Singular Geometry of Low-Rank Adaptation

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The paper investigates the singular statistical nature of Low‑Rank Adaptation (LoRA), a popular parameter‑efficient fine‑tuning method for large neural networks. By applying the real log canonical threshold (RLCT) from singular learning theory, the authors analyze how LoRA’s learning complexity depends on its low‑rank factorization and the pretrained network. They show that the forward‑backward covariance, derived from activations and backpropagated sensitivities, governs which low‑rank perturbations are statistically observable, leading to a detailed characterization of the model’s singular geometry both locally and globally, and introduce a curvature‑corrected estimator for the RLCT.

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