arXiv Machine Learning

Uniform Discrete Diffusion Models are Minimax Optimal for Estimating Distributions with Small Effective Support Size

arXiv Machine Learning
Sep 18

Parallelism, critical windows, and separations among diffusion language models

The paper compares the parallelism capabilities of three diffusion large language model paradigms—masked, uniform, and Gaussian diffusion. It proves that uniform and Gaussian diffusion can sample with a number of forward passes scaling with the dual total correlation of the distribution, potentially much less than the context length, whereas masked diffusion may require more passes. The study establishes a provable separation in parallelism, showing that masked diffusion’s critical windows are asymptotically narrower than those of the other two approaches.

By Sitan Chen, Liye Wang
arXiv Statistics ML
Oct 5

KL Convergence Guarantees for Score diffusion models under minimal data assumptions

The paper presents new Kullback–Leibler convergence guarantees for score diffusion models that avoid restrictive Lipschitz assumptions on the score function. By analyzing models with fixed step size derived from the Ornstein–Uhlenbeck semigroup and its kinetic counterpart, the authors derive simple, sharp KL bounds that hold for any data distribution with finite Fisher information relative to the standard Gaussian. This extends theoretical guarantees to a broader class of data distributions without requiring early stopping or compact support.

By Giovanni Conforti, Alain Durmus, Marta Gentiloni Silveri
arXiv Machine Learning
2d ago

Transformer-Based Masked Diffusion Models Provably Learn Distributions with Latent Structure

Masked diffusion models (MDMs) generate discrete data by iteratively unmasking multiple tokens in parallel using a learned mask predictor. The paper provides end‑to‑end statistical guarantees for transformer‑based MDMs, showing that when the data distribution is well approximated by mixtures of hidden Markov trees, the model can achieve ε‑accurate sampling in KL divergence with ∫O(LK_par/ε) training samples, where K_par is polynomial in the sequence length, vocabulary size, number of hidden states, and mixture components. The transformer network and sampling procedure adapt automatically to the unknown latent structure without requiring prior knowledge of tree topologies or component parameters.

By Jingda Wu, Changxiao Cai
arXiv AI
Jun 8

A Temporal Spatial Minimax Rate for Smoothly-Varying Distributions in Wasserstein Space

arXiv:2606. 07325v1 Announce Type: cross Abstract: We study the minimax rate of estimating a future value $\mu_{t_n+h}$ of a curve $t\mapsto\mu_t$ in the $2$-Wasserstein space $\mathcal{P}_2(\mathbb{R}^d)$ from finitely many noisy snapshots of its past, under an adiabatic bound $\|\nabla_t^k v\|\le\varepsilon$ on the $k$-th covariant derivative of the velocity field.

By Munsik Kim