Search Results for author: Nicolas Boullé

Found 14 papers, 6 papers with code

Multiplicative Dynamic Mode Decomposition

no code implementations8 May 2024 Nicolas Boullé, Matthew J. Colbrook

Koopman operators are infinite-dimensional operators that linearize nonlinear dynamical systems, facilitating the study of their spectral properties and enabling the prediction of the time evolution of observable quantities.

Operator learning without the adjoint

1 code implementation31 Jan 2024 Nicolas Boullé, Diana Halikias, Samuel E. Otto, Alex Townsend

There is a mystery at the heart of operator learning: how can one recover a non-self-adjoint operator from data without probing the adjoint?

Operator learning

On the Convergence of Hermitian Dynamic Mode Decomposition

no code implementations6 Jan 2024 Nicolas Boullé, Matthew J. Colbrook

We show that, under suitable conditions, the eigenvalues and eigenfunctions of HDMD converge to the spectral properties of the underlying Koopman operator.

A Mathematical Guide to Operator Learning

no code implementations22 Dec 2023 Nicolas Boullé, Alex Townsend

We explain the types of problems and PDEs amenable to operator learning, discuss various neural network architectures, and explain how to employ numerical PDE solvers effectively.

Operator learning

Elliptic PDE learning is provably data-efficient

1 code implementation24 Feb 2023 Nicolas Boullé, Diana Halikias, Alex Townsend

PDE learning is an emerging field that combines physics and machine learning to recover unknown physical systems from experimental data.

Data-driven discovery of Green's functions

1 code implementation28 Oct 2022 Nicolas Boullé

Finally, theoretical results on Green's functions and rational NNs are combined to design a human-understandable deep learning method for discovering Green's functions from data.

Learning Green's functions associated with time-dependent partial differential equations

no code implementations27 Apr 2022 Nicolas Boullé, Seick Kim, Tianyi Shi, Alex Townsend

Neural operators are a popular technique in scientific machine learning to learn a mathematical model of the behavior of unknown physical systems from data.

A generalization of the randomized singular value decomposition

no code implementations ICLR 2022 Nicolas Boullé, Alex Townsend

The randomized singular value decomposition (SVD) is a popular and effective algorithm for computing a near-best rank $k$ approximation of a matrix $A$ using matrix-vector products with standard Gaussian vectors.

Data-driven discovery of Green's functions with human-understandable deep learning

2 code implementations1 May 2021 Nicolas Boullé, Christopher J. Earls, Alex Townsend

There is an opportunity for deep learning to revolutionize science and technology by revealing its findings in a human interpretable manner.

Accurate numerical simulation of electrodiffusion and water movement in brain tissue

no code implementations4 Feb 2021 Ada J. Ellingsrud, Nicolas Boullé, Patrick E. Farrell, Marie E. Rognes

Mathematical modelling of ionic electrodiffusion and water movement is emerging as a powerful avenue of investigation to provide new physiological insight into brain homeostasis.

Numerical Analysis Computational Engineering, Finance, and Science Numerical Analysis

Learning elliptic partial differential equations with randomized linear algebra

no code implementations31 Jan 2021 Nicolas Boullé, Alex Townsend

Given input-output pairs of an elliptic partial differential equation (PDE) in three dimensions, we derive the first theoretically-rigorous scheme for learning the associated Green's function $G$.

Rational neural networks

3 code implementations NeurIPS 2020 Nicolas Boullé, Yuji Nakatsukasa, Alex Townsend

We consider neural networks with rational activation functions.

Classification of chaotic time series with deep learning

no code implementations26 Jul 2019 Nicolas Boullé, Vassilios Dallas, Yuji Nakatsukasa, D. Samaddar

We use standard deep neural networks to classify univariate time series generated by discrete and continuous dynamical systems based on their chaotic or non-chaotic behaviour.

Classification General Classification +3

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