作者：Zhenghua Luo , Bentuo Zheng 来源：[J].Studia Mathematica(IF 0.549), 2020, Vol.250, pp.19-34IMPAS 摘要：A normed space $X$ is said to have the ball-covering property (BCP,for short) if its unit sphere can be covered by the union of countablymany closed balls not containing the origin. Let $(\varOmega, \varSigma, \mu)$ bea separable measure space and $X$ be a normed space. We show t...
 作者：Dongyang Chen , William B. Johnson , Bentuo Zheng 来源：[J].Studia Mathematica(IF 0.549), 2014, Vol.223, pp.187-191IMPAS 摘要：We give a corrected proof of Theorem 2.10 in our paper “Commutators on $(\sum \ell _q)_p$” [Studia Math. 206 (2011),175–190] for the case $1< q< p< \infty$. The case when $1=q< p< \infty$ remains open. As a consequence, the Main Theorem and Corollary 2.17 in that pape...
 作者：Bentuo Zheng 来源：[J].Studia Mathematica(IF 0.549), 2006, Vol.176, pp.177-190IMPAS 摘要：Let $1< p< \infty$. Let $X$ be a subspace of a space $Z$ witha shrinking F.D.D. $(E_n)$ which satisfies a block lower-$p$estimate. Then any bounded linear operator $T$ from $X$ whichsatisfies an upper-$(C,p)$-tree estimate factors through asubspace of $(\sum F_n)_{l_p}$, where $(...  作者：Bentuo Zheng 来源：[J].Studia Mathematica(IF 0.549), 2008, Vol.185, pp.87-98IMPAS 摘要：Let$1< q< p< \infty$and$q\leq r\leq p$. Let$X$be a reflexive Banach space satisfying a lower-$\ell_q$-tree estimate and let$T$be a bounded linear operator from$X$which satisfies an upper-$\ell_p$-tree estimate. Then$T$factors through a subspace of$(\sum F_n)_{\ell_r}$...  作者：Dongyang Chen , William B. Johnson , Bentuo Zheng 来源：[J].Studia Mathematica(IF 0.549), 2011, Vol.206, pp.175-190IMPAS 摘要：Let$T$be a bounded linear operator on$X=(\sum \ell_{q})_{{p}}$with$1\le q < \infty$and$1< p< \infty$. Then$T$is a commutator if and only if for all non-zero$\lambda\in \mathbb{C}$, the operator$T-\lambda I$is not$X\$-strictly singular.