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arXiv 0705.2253math.PR
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关于矩阵上Kac随机游动的平衡点收敛性

On the convergence to equilibrium of Kac's random walk on matrices

Roberto Imbuzeiro Oliveira

摘要:

我们考虑Kac的随机游动$n$维旋转矩阵,其中每一步是一个随机旋转的平面上产生的两个随机挑选的坐标。我们表明,这个过程收敛到Haar措施$\mathit{SO}(n)$在$L^2$运输成本(Wasserstein)度量在$O(n^2\ln n)$步骤。我们还证明了我们的界限是最多一个$O(\ln n)$因素远离最优。以前的边界,由于Diaconis/Saloff-Coste和Pak/Sjorko,有额外的权力$n$和举行只为$L^1$运输成本。我们的证明方法包括一个独立的利益,类似于Bubley和Dyer的路径耦合方法的一般结果。设$P$是波兰长度空间$(M,d)$上的马氏链,且对所有具有$d(x,y)\ll1$的$x,y\in M$,都存在一个从$x$到$y$的一步$P$的耦合$(X,Y)$.平均以$(ξ+o(1))$因子收缩距离。则映射$μ\mapstoμP$是$ξ$ -在运输成本度量中收缩。

英文摘要:

We consider Kac's random walk on $n$-dimensional rotation matrices, where each step is a random rotation in the plane generated by two randomly picked coordinates. We show that this process converges to the Haar measure on $\mathit{SO}(n)$ in the $L^2$ transportation cost (Wasserstein) metric in $O(n^2\ln n)$ steps. We also prove that our bound is at most a $O(\ln n)$ factor away from optimal. Previous bounds, due to Diaconis/Saloff-Coste and Pak/Sidenko, had extra powers of $n$ and held only for $L^1$ transportation cost. Our proof method includes a general result of independent interest, akin to the path coupling method of Bubley and Dyer. Suppose that $P$ is a Markov chain on a Polish length space $(M,d)$ and that for all $x,y\in M$ with $d(x,y)\ll1$ there is a coupling $(X,Y)$ of one step of $P$ from $x$ and $y$ (resp.) that contracts distances by a $(ξ+o(1))$ factor on average. Then the map $μ\mapstoμP$ is $ξ$-contracting in the transportation cost metric.

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