On Qian's problem for ${\mathcal{L}}_{\infty }$-spaces

Abstract

In this paper we devote to study Qian's problem for ${\mathcal{L}}_{\infty }$-spaces. Firstly, a positive answer to Qian's problem for $C(K)$-spaces is given by the assumption that $K$ has the C$\check{e}$ch-Stone property. Secondly, we obtain quantitative characterizations of separably injective spaces that turn out to give a positive answer to Qian's problem of 1995 in the setting of separable universality. Thirdly, we prove a sharpen quantitative and generalized Sobczyk theorem, which gives sharpen constants ($\alpha ,\gamma$) for Qian's Problem. Finally, we give a more generalized Figiel theorem for ${\mathcal{L}}_{\infty }$-spaces.

18 pages. This is a part of the author's Ph. D. Thesis

References in corpus (3)

• Stability of Banach spaces via nonlinear $\epsilon$-isometries
• On universal left-stability of $\epsilon$-isometries
• Universal stability of Banach spaces for $\epsilon$-isometries