揭示了生成模型在低维流形上的理论生成速率,突破高维空间的瓶颈。
Intrinsic Wasserstein Rates for Score-Based Generative Models on Smooth Manifolds
- 基于流形上最近投影坐标实现分数网络的显式构造
- 达到与流形维度相关的最优Wasserstein-1收敛率 $\tilde{\mathcal{O}}(n^{-(β+1)/(d+2β)})$
- 适用于具有光滑几何结构和密度下界的低维数据分布
分数生成模型在高维环境空间中训练,但许多数据分布支持于低维非线性结构。本文证明,对于定义在 $[0,1]^D$ 中的紧致 $d$-维光滑流形 $\mathcal{M}$($d > 2$)且具有严格正的 $β$-Hölder 密度的情况,方差保持的 SGM 估计器可达内在 Wasserstein-1 样本指数 $\tilde{\mathcal{O}}(D^{\mathcal{O}_β(d)}n^{-(β+1)/(d+2β)})$,包含对数因子及几何、密度相关常数。全非渐近界明确分离出有限阶几何包络、Hölder半径、密度下界、环境依赖及有限阶修正项。分析将分数逼近分解为大噪声切胞区与小噪声投影中心、去高斯化拉普拉斯区。关键技术是通过有限内在锚点与 Gauss–Newton 迭代实现 ReLU 型最近投影坐标,而非将流形投影视为黑箱高维平滑映射。因此,对于几何与密度下界多项式控制的族,构造的分数网络参数具有多项式环境依赖性。
原文摘要 · Abstract (English)
Score-based generative models are trained in high-dimensional ambient spaces, yet many data distributions are supported on low-dimensional nonlinear structures. We prove that, for compact $d$-dimensional smooth manifolds $\mathcal{M} \subset [0,1]^D$ with $d > 2$ and $β$-Hölder densities strictly positive on $\mathcal{M}$, a variance-preserving SGM estimator attains the intrinsic Wasserstein--1 sample exponent $\tilde{\mathcal{O}}(D^{\mathcal{O}_β(d)}n^{-(β+1)/(d+2β)})$, up to logarithmic factors and explicit geometry and density factors. The full nonasymptotic bound explicitly isolates the finite-order geometry envelope, Hölder radius, density lower bound, ambient dependence, and finite-order correction terms. The analysis separates score approximation into a large-noise tangent-cell regime and a small-noise projection-centered, de-Gaussianized Laplace regime. The key technical ingredient is a ReLU implementation of nearest-projection coordinates via finite intrinsic anchors and Gauss--Newton iterations, rather than approximating the manifold projection as a black-box high-dimensional smooth map. Consequently, for families with polynomially controlled geometry and density lower bounds, the constructed score-network parameters have polynomial ambient dependence.
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