Understanding the dimension dependency of computational complexity in high-dimensional sampling problem is a fundamental problem, both from a practical and theoretical perspective. Compared with samplers with unbiased stationary distribution, e.g., Metropolis-adjusted Langevin algorithm (MALA), biased samplers, e.g., Underdamped Langevin Dynamics (ULD), perform better in low-accuracy cases just because a lower dimension dependency in their complexities. Along this line, Freund et al. (2022) suggest that the modified Langevin algorithm with prior diffusion is able to converge dimension independently for strongly log-concave target distributions. Nonetheless, it remains open whether such property establishes for more general cases. In this paper, we investigate the prior diffusion technique for the target distributions satisfying log-Sobolev inequality (LSI), which covers a much broader class of distributions compared to the strongly log-concave ones. In particular, we prove that the modified Langevin algorithm can also obtain the dimension-independent convergence of KL divergence with different step size schedules. The core of our proof technique is a novel construction of an interpolating SDE, which significantly helps to conduct a more accurate characterization of the discrete updates of the overdamped Langevin dynamics. Our theoretical analysis demonstrates the benefits of prior diffusion for a broader class of target distributions and provides new insights into developing faster sampling algorithms.

在这篇论文中，我们研究了应用于满足对数Sobolev不等式（LSI）的目标分布的先验扩散技术，证明了改进的 Langevin 算法在不同步长计划下能够获得与维度无关的 KL 散度收敛，并通过构建插值的 SDE 和准确描述过阻尼 Langevin 动力学离散更新的方法提供了理论分析的证明。我们的研究结果展示了先验扩散对更广泛类别的目标分布的优势，并为开发更快的采样算法提供了新的见解。

基于先验扩散的Langevin算法在非对数凹采样问题中的改进分析