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arXiv math/0512382math.PR
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(上)鞅的正规控制

Normal domination of (super)martingales

Iosif Pinelis

摘要:

设(S_0,S_1,.)是关于σ-代数(H_{\le0},H_{\le1},.)的非减序列的上鞅,用S_0 \le 0几乎肯定(a.s.)以及差X_i =S_i- S_{i-1}。假设对于每个i= 1,2,.存在H_{\le(i-1)} -可测量的r. v.的C_{i-1}和D_{i-1}以及正实数s_i,使得C_{i-1} \le X_i \le D_{i-1}和D_{i-1} - C_{i-1} \le 2 s_i a.s.则对于所有实数t和自然数n,有\E f_t(S_n)\le \E f_t(sZ),其中f_t(x):= \max(0,x-t)^5,s:= \sqrt{s_1^2+...+s_n^2},Z是N(0,1)。特别地,这意味着对于\R中的所有x,P(S_n \ge x)\le c_{5,0} P(Z \ge x/s),其中c_{5,0} =5!(e/5)^5=5.699.... \max_{0\le k\le n} S_k代替S_n和测量浓度的结果也如下。

英文摘要:

Let (S_0,S_1,...) be a supermartingale relative to a nondecreasing sequence of σ-algebras (H_{\le0},H_{\le1},...), with S_0\le0 almost surely (a.s.) and differences X_i:=S_i-S_{i-1}. Suppose that for every i=1,2,... there exist H_{\le(i-1)}-measurable r.v.'s C_{i-1} and D_{i-1} and a positive real number s_i such that C_{i-1}\le X_i\le D_{i-1} and D_{i-1}-C_{i-1}\le 2 s_i a.s. Then for all real t and natural n one has \E f_t(S_n)\le\E f_t(sZ), where f_t(x):=\max(0,x-t)^5, s:=\sqrt{s_1^2+...+s_n^2}, and Z is N(0,1). In particular, this implies P(S_n\ge x)\le c_{5,0}P(Z\ge x/s) for all x in \R, where c_{5,0}=5!(e/5)^5=5.699.... Results for \max_{0\le k\le n}S_k in place of S_n and for concentration of measure also follow.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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