Numerical Methods for Dynamical Low-Rank Approximations of Stochastic Differential Equations -- Part I: Time discretization

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Main Authors: Kazashi, Yoshihito, Nobile, Fabio, Zoccolan, Fabio
Format: Preprint
Published: 2026
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author Kazashi, Yoshihito
Nobile, Fabio
Zoccolan, Fabio
author_facet Kazashi, Yoshihito
Nobile, Fabio
Zoccolan, Fabio
contents In this work (Part I), we study three time-discretization procedures of the Dynamical Low-Rank Approximation (DLRA) of high-dimensional stochastic differential equations (SDEs). Specifically, we consider the Dynamically Orthogonal (DO) method for DLRA proposed and analyzed in arXiv:2308.11581v4, which consists of a linear combination of products between deterministic orthonormal modes and stochastic modes, both time-dependent. The first strategy we consider for numerical time-integration is very standard, consisting in a forward discretization in time of both deterministic and stochastic components. Its convergence is proven subject to a time-step restriction dependent on the smallest singular value of the Gram matrix associated to the stochastic modes. Under the same condition on the time-step, this smallest singular value is shown to be always positive, provided that the SDE under study is driven by a non-degenerate noise. The second and the third algorithms, on the other hand, are staggered ones, in which we alternately update the deterministic and the stochastic modes in half steps. These approaches are shown to be more stable than the first one and allow us to obtain convergence results without the aforementioned restriction on the time-step. Computational experiments support theoretical results. In this work we do not consider the discretization in probability, which will be the topic of Part II.
format Preprint
id arxiv_https___arxiv_org_abs_2601_21428
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Numerical Methods for Dynamical Low-Rank Approximations of Stochastic Differential Equations -- Part I: Time discretization
Kazashi, Yoshihito
Nobile, Fabio
Zoccolan, Fabio
Numerical Analysis
60H10, 60H35, 65C30
In this work (Part I), we study three time-discretization procedures of the Dynamical Low-Rank Approximation (DLRA) of high-dimensional stochastic differential equations (SDEs). Specifically, we consider the Dynamically Orthogonal (DO) method for DLRA proposed and analyzed in arXiv:2308.11581v4, which consists of a linear combination of products between deterministic orthonormal modes and stochastic modes, both time-dependent. The first strategy we consider for numerical time-integration is very standard, consisting in a forward discretization in time of both deterministic and stochastic components. Its convergence is proven subject to a time-step restriction dependent on the smallest singular value of the Gram matrix associated to the stochastic modes. Under the same condition on the time-step, this smallest singular value is shown to be always positive, provided that the SDE under study is driven by a non-degenerate noise. The second and the third algorithms, on the other hand, are staggered ones, in which we alternately update the deterministic and the stochastic modes in half steps. These approaches are shown to be more stable than the first one and allow us to obtain convergence results without the aforementioned restriction on the time-step. Computational experiments support theoretical results. In this work we do not consider the discretization in probability, which will be the topic of Part II.
title Numerical Methods for Dynamical Low-Rank Approximations of Stochastic Differential Equations -- Part I: Time discretization
topic Numerical Analysis
60H10, 60H35, 65C30
url https://arxiv.org/abs/2601.21428