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On learning higher-order cumulants in diffusion models

Gert Aarts Orcid Logo, Diaa Eddin Habibi, Lingxiao Wang Orcid Logo, Kai Zhou Orcid Logo

Machine Learning: Science and Technology, Volume: 6, Issue: 2, Start page: 025004

Swansea University Authors: Gert Aarts Orcid Logo, Diaa Eddin Habibi

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Abstract

To analyse how diffusion models learn correlations beyond Gaussian ones, we study the behaviour of higher-order cumulants, or connected n-point functions, under both the forward and backward process. We derive explicit expressions for the moment- and cumulant-generating functionals, in terms of the...

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Published in: Machine Learning: Science and Technology
ISSN: 2632-2153
Published: IOP Publishing 2025
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa69229
Abstract: To analyse how diffusion models learn correlations beyond Gaussian ones, we study the behaviour of higher-order cumulants, or connected n-point functions, under both the forward and backward process. We derive explicit expressions for the moment- and cumulant-generating functionals, in terms of the distribution of the initial data and properties of forward process. It is shown analytically that during the forward process higher-order cumulants are conserved in models without a drift, such as the variance-expanding scheme, and that therefore the endpoint of the forward process maintains nontrivial correlations. We demonstrate that since these correlations are encoded in the score function, higher-order cumulants are learnt in the backward process, also when starting from a normal prior. We confirm our analytical results in an exactly solvable toy model with nonzero cumulants and in scalar lattice field theory.
Keywords: learning, cumulants, lattice field theory, diffusion models
College: Faculty of Science and Engineering
Funders: GAis supported by STFC Consolidated Grant ST/X000648/1. DEH is supported by the UKRI AIMLAC CDT EP/S023992/1. We thanks the DEEP-IN working group at RIKEN-iTHEMS for its support in the preparation of this paper. LW is also supported by the RIKEN TRIP initiative (RIKEN Quantum) and JST-BOOST Grant (No. 24036419). KZ is supported by the CUHK-Shenzhen university development fund under Grant Nos. UDF01003041 and UDF03003041, and Shenzhen Peacock fund under No. 2023TC0179. Weacknowledge the support of the Supercomputing Wales project, which is part-funded by the European Regional Development Fund (ERDF) via Welsh Government.
Issue: 2
Start Page: 025004