Work

Nonlinear kinetic closures for linear instabilities

Year: 2026

Type: preprint

Abstract: Landau fluid closures are linear in the evolved moments. We examine the consequences of relaxing linearity. As an example, we introduce the nonlinear exact kinetic response closure, exact on an eigenmode but not on superpositions. A counting argument shows that a closure on $N$ instantaneous moments and the field can represent at most $(N+1)/2$ superposed eigenmodes. Guided by this, we train an equivariant neural-network and a learned Padé closure on analytic data. For bump-on-tail and slab ITG instabilities they reduce growth-rate errors by up to three orders of magnitude over Landau closures.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2609.17209

Authors: Paul, Elizabeth J., Joglekar, Archis, Knyazev, Alexey

Institutions: Columbia University, Ergodic LLC (United States)

Topic: Magnetic confinement fusion research

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, U.S. Department of Energy

Awards: Institute for Pure and Applied Mathematics, Institute for Pure and Applied Mathematics, G4139577858, G4896746546, G5062748268, Collaborative Research: Wave-Particle Interactions in 3D Magnetic Fields, G586700770, G5901874495, G663282964, G969889393

OpenAlex ID: W7213394022

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