Permutation-Symmetrized Diffusion for Unconditional Molecular Generation

Fuente: arXiv
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Autori principali: Ko, Gyeonghoon, Lee, Juho
Natura: Preprint
Pubblicazione: 2026
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author Ko, Gyeonghoon
Lee, Juho
author_facet Ko, Gyeonghoon
Lee, Juho
contents Permutation invariance is fundamental in molecular point-cloud generation, yet most diffusion models enforce it indirectly via permutation-equivariant networks on an ordered space. We propose to model diffusion directly on the quotient manifold $\tilde{\calX}=\sR^{d\times N}/S_N$, where all atom permutations are identified. We show that the heat kernel on $\tilde{\calX}$ admits an explicit expression as a sum of Euclidean heat kernels over permutations, which clarifies how diffusion on the quotient differs from ordered-particle diffusion. Training requires a permutation-symmetrized score involving an intractable sum over $S_N$; we derive an expectation form over a posterior on permutations and approximate it using MCMC in permutation space. We evaluate on unconditional 3D molecule generation on QM9 under the EQGAT-Diff protocol, using SemlaFlow-style backbone and treating all variables continuously. The results demonstrate that quotient-based permutation symmetrization is practical and yields competitive generation quality with improved efficiency.
format Preprint
id arxiv_https___arxiv_org_abs_2603_23255
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Permutation-Symmetrized Diffusion for Unconditional Molecular Generation
Ko, Gyeonghoon
Lee, Juho
Machine Learning
Permutation invariance is fundamental in molecular point-cloud generation, yet most diffusion models enforce it indirectly via permutation-equivariant networks on an ordered space. We propose to model diffusion directly on the quotient manifold $\tilde{\calX}=\sR^{d\times N}/S_N$, where all atom permutations are identified. We show that the heat kernel on $\tilde{\calX}$ admits an explicit expression as a sum of Euclidean heat kernels over permutations, which clarifies how diffusion on the quotient differs from ordered-particle diffusion. Training requires a permutation-symmetrized score involving an intractable sum over $S_N$; we derive an expectation form over a posterior on permutations and approximate it using MCMC in permutation space. We evaluate on unconditional 3D molecule generation on QM9 under the EQGAT-Diff protocol, using SemlaFlow-style backbone and treating all variables continuously. The results demonstrate that quotient-based permutation symmetrization is practical and yields competitive generation quality with improved efficiency.
title Permutation-Symmetrized Diffusion for Unconditional Molecular Generation
topic Machine Learning
url https://arxiv.org/abs/2603.23255