A Nonlinear Separation Principle via Contraction Theory: Applications to Neural Networks, Control, and Learning

Fuente: arXiv
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Main Authors: Gokhale, Anand, Proskurnikov, Anton V., Kawano, Yu, Bullo, Francesco
Format: Preprint
Published: 2026
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author Gokhale, Anand
Proskurnikov, Anton V.
Kawano, Yu
Bullo, Francesco
author_facet Gokhale, Anand
Proskurnikov, Anton V.
Kawano, Yu
Bullo, Francesco
contents This paper establishes a nonlinear separation principle based on contraction theory and derives sharp stability conditions for recurrent neural networks (RNNs). First, we introduce a nonlinear separation principle that guarantees global exponential stability for the interconnection of a contracting state-feedback controller and a contracting observer, alongside parametric extensions for robustness and equilibrium tracking. Second, we derive sharp linear matrix inequality (LMI) conditions that guarantee the contractivity of both firing rate and Hopfield neural network architectures. We establish structural relationships among these certificates-demonstrating that continuous-time models with monotone non-decreasing activations maximize the admissible weight space-and extend these stability guarantees to interconnected systems and Graph RNNs. Third, we combine our separation principle and LMI framework to solve the output reference tracking problem for RNN-modeled plants. We provide LMI synthesis methods for feedback controllers and observers, and rigorously design a low-gain integral controller to eliminate steady-state error. Finally, we derive an exact, unconstrained algebraic parameterization of our contraction LMIs to design highly expressive implicit neural networks, achieving competitive accuracy and parameter efficiency on standard image classification benchmarks.
format Preprint
id arxiv_https___arxiv_org_abs_2604_15238
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A Nonlinear Separation Principle via Contraction Theory: Applications to Neural Networks, Control, and Learning
Gokhale, Anand
Proskurnikov, Anton V.
Kawano, Yu
Bullo, Francesco
Systems and Control
Machine Learning
Optimization and Control
This paper establishes a nonlinear separation principle based on contraction theory and derives sharp stability conditions for recurrent neural networks (RNNs). First, we introduce a nonlinear separation principle that guarantees global exponential stability for the interconnection of a contracting state-feedback controller and a contracting observer, alongside parametric extensions for robustness and equilibrium tracking. Second, we derive sharp linear matrix inequality (LMI) conditions that guarantee the contractivity of both firing rate and Hopfield neural network architectures. We establish structural relationships among these certificates-demonstrating that continuous-time models with monotone non-decreasing activations maximize the admissible weight space-and extend these stability guarantees to interconnected systems and Graph RNNs. Third, we combine our separation principle and LMI framework to solve the output reference tracking problem for RNN-modeled plants. We provide LMI synthesis methods for feedback controllers and observers, and rigorously design a low-gain integral controller to eliminate steady-state error. Finally, we derive an exact, unconstrained algebraic parameterization of our contraction LMIs to design highly expressive implicit neural networks, achieving competitive accuracy and parameter efficiency on standard image classification benchmarks.
title A Nonlinear Separation Principle via Contraction Theory: Applications to Neural Networks, Control, and Learning
topic Systems and Control
Machine Learning
Optimization and Control
url https://arxiv.org/abs/2604.15238