Volume 22 , Issue 2 , December 2020 , Pages 143-148
Pshtiwan Sabir Nouri 1 ; Mudhafar Fattah Hama 2
1 Department of Mathematics, College of Computer Science and Mathematics, Tikrit University , Iraq.
2 Department of Mathematics, College of Science, University of Sulaimani, Sulaimani, Kurdistan Region- Iraq
The main purpose of this article is to answer the Plichko's question; let X be any Banach space and Γ⊂X* be any total set if Ba(X; σ(X; Γ)) =Ba(X; weak); then does imply every weakly* sequentially closed sub-space of X* is weakly* closed? Also, answer the question: Let A ⊆X* such that A is convex and bounded and for each element a ∈ \overline{A}weak* then a ∈ \overline{B}weak* for a countable subset B of A; Then does it imply (X; σ(X; Γ)) =Ba(X;weak) ?