数学物理学报(英文版) ›› 2012, Vol. 32 ›› Issue (4): 1627-1636.doi: 10.1016/S0252-9602(12)60129-5

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DOUBLE Φ-INEQUALITIES FOR BANACH-SPACE-VALUED MARTINGALES

王迎占1,2|张超1|侯友良1*   

  1. 1. School of Mathematics and Statistics, Wuhan University, Wuhan 430072, China;
    2. College of Mathematics and Information Sciences, Guangzhou University, Guangzhou 510006, China
  • 收稿日期:2010-08-20 修回日期:2011-07-07 出版日期:2012-07-20 发布日期:2012-07-20
  • 通讯作者: 侯友良,ylhou323@whu.edu.cn E-mail:wyzde@tom.com; zaoyangzhangchao@163.com; ylhou323@whu.edu.cn
  • 基金资助:

    This research was supported by the National Natural Science Foundation of China (11071190).

DOUBLE Φ-INEQUALITIES FOR BANACH-SPACE-VALUED MARTINGALES

 WANG Ying-Zhan1,2, ZHANG Chao1, HOU You-Liang1*   

  1. 1. School of Mathematics and Statistics, Wuhan University, Wuhan 430072, China;
    2. College of Mathematics and Information Sciences, Guangzhou University, Guangzhou 510006, China
  • Received:2010-08-20 Revised:2011-07-07 Online:2012-07-20 Published:2012-07-20
  • Contact: HOU You-Liang,ylhou323@whu.edu.cn E-mail:wyzde@tom.com; zaoyangzhangchao@163.com; ylhou323@whu.edu.cn
  • Supported by:

    This research was supported by the National Natural Science Foundation of China (11071190).

摘要:

Let B be a Banach space, Φ1, Φ2 be two generalized convex Φ-functions and  ψ1, ψ2 the Young complementary functions of Φ1, Φ2 respectively with
tt0ψ2(s)/s dsc0 ψ1(c0t) (t > t0)
for some constants c0 > 0 and t0 > 0, where  ψ1 and ψ2 are the left-continuous derivative functions of  ψ1 and ψ2, respectively. We claim that: (i) If B is isomorphic to a p-uniformly smooth space (or q-uniformly convex space, respectively), then there exists a constant c > 0 such that for any B-valued martingale f = (fn)n≥0,

||f *||Φ1c||S(p)(f)||Φ2 (or ||S(q)(f)||Φ1c||f *||Φ2 , respectively),

where f * and S(p)(f) are the maximal function and the p-variation function of f respec-tively; (ii) If B is a UMD space, Tvf is the martingale transform of f with respect to v = (vn)n≥0 (v* ≤ 1), then ||(Tvf )||Φ1c||f *||Φ2 .

关键词: martingale, convex Φ-inequality, martingale transform, weighted average

Abstract:

Let B be a Banach space, Φ1, Φ2 be two generalized convex Φ-functions and  ψ1, ψ2 the Young complementary functions of Φ1, Φ2 respectively with
tt0ψ2(s)/s dsc0 ψ1(c0t) (t > t0)
for some constants c0 > 0 and t0 > 0, where  ψ1 and ψ2 are the left-continuous derivative functions of  ψ1 and ψ2, respectively. We claim that: (i) If B is isomorphic to a p-uniformly smooth space (or q-uniformly convex space, respectively), then there exists a constant c > 0 such that for any B-valued martingale f = (fn)n≥0,

||f *||Φ1c||S(p)(f)||Φ2 (or ||S(q)(f)||Φ1c||f *||Φ2 , respectively),

where f * and S(p)(f) are the maximal function and the p-variation function of f respec-tively; (ii) If B is a UMD space, Tvf is the martingale transform of f with respect to v = (vn)n≥0 (v* ≤ 1), then ||(Tvf )||Φ1c||f *||Φ2 .

Key words: martingale, convex Φ-inequality, martingale transform, weighted average

中图分类号: 

  • 60G42