某些齐性空间上随机游走的多切片与有效均匀分布
Multislicing and effective equidistribution for random walks on some homogeneous spaces
AI总结:
研究 SO(2,1) 或 SO(3,1) 齐性空间上由 Zariski 稠密子群驱动的随机游走,证明非陷阱起始点的 n 步分布均匀收敛于 Haar 测度,并在算术假设下得到指数收敛率,核心创新在于引入多切片现象。
摘要:
我们考虑齐性空间 $G/Λ$ 上的随机游走,其中 $G$ 为 $\mathrm{SO}(2,1)$ 或 $\mathrm{SO}(3,1)$,$Λ$ 为格点。游走由 $G$ 上的概率测度 $μ$ 驱动,其支撑生成 Zariski 稠密子群。我们证明,对于每个不被困在有限 $μ$-不变集中的起点 $x \in G/Λ$,游走的 $n$ 步分布 $μ^{*n}*δ_{x}$ 均匀分布到 Haar 测度。此外,在 $(Λ, μ)$ 的算术假设下,我们证明收敛以指数速率发生,其速度受限于 $x$ 可能处于尖点高处或靠近有限轨道的障碍。我们的方法与 Benoist-Quint 的方法有本质不同,后者的均匀分布陈述仅在 Cesàro 平均下成立且非定量;也与 Bourgain-Furman-Lindenstrauss-Mozes 关于环面情形的结果以及 Lindenstrauss-Mohammadi-Wang 和 Yang 关于单幂流的类似问题的方法不同。我们证明的一个关键新特征是使用了我们称之为多切片的新现象。后者是 Bourgain 等人离散投影定理的推广,我们相信它具有独立的意义。
英文摘要:
We consider a random walk on a homogeneous space $G/Λ$ where $G$ is $\mathrm{SO}(2,1)$ or $\mathrm{SO}(3,1)$ and $Λ$ is a lattice. The walk is driven by a probability measure $μ$ on $G$ whose support generates a Zariski-dense subgroup. We show that for every starting point $x \in G/Λ$ which is not trapped in a finite $μ$-invariant set, the $n$-step distribution $μ^{*n}*δ_{x}$ of the walk equidistributes toward the Haar measure. Moreover, under arithmetic assumptions on the pair $(Λ, μ)$, we show the convergence occurs at an exponential rate, tempered by the obstructions that $x$ may be high in a cusp or close to a finite orbit. Our approach is substantially different from that of Benoist-Quint, whose equidistribution statements only hold in Cesàro average and are not quantitative, that of Bourgain-Furman-Lindenstrauss-Mozes concerning the torus case, and that of Lindenstrauss-Mohammadi-Wang and Yang about the analogous problem for unipotent flows. A key new feature of our proof is the use of a new phenomenon which we call multislicing. The latter is a generalization of the discretized projection theorems à la Bourgain and we believe it presents independent interest.
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